A quick overview...
Strengths: Basketball IQ, Vision, passing Ability, NBA body (besides standing reach), scoring in transition, distributing/leading in transition, ability to run an offense like a traditional point-guard, athleticism, good hands on defense, natural nose for the boards, slashing (when given the appropriate spacing), offensive rebounding, truly ambidextrous with the ball, by all accounts is a great guy in the locker-room (don't buy the bullshit fools like Tim Brando are selling), and has the commitment to improve me himself over the course of his career.
Weaknesses: jump shooting, three-point shooting, post defense, takes bad fouls on both sides of the ball, boxing out with consistency, scoring instincts, length (8'7" standing reach is a low measurement for his height),
Somewhere in the middle and in need of improvement: shot-blocking, anticipation/defensive awareness, use of his body on defense, understanding when to attack with great positioning in the post, being decisive with the ball, post moves, mid-range scoring, free-throw shooting, over-passing, touch around the basket, defensive rebounding (gets positioning but doesn't battle or drive his man backwards, very soft/non-existent box-outs towards the end of the year.)
Where he was hamstrung by his coach/system/teammates this year: SPACING! No great offensive player can do their thing without spacing, this was the true knock against Jones half-court system. It provided/manufactured no spacing for Simmons, who regularly had to go 2 or 3 on 1 on slashes to the rim. He was also pretty much consummately playing two steps ahead of everyone else on the floor, which resulted in some miscommunication turnovers early in the season, and then as a result of those missed connections, a hesitance to go for riskier passes later in the year (I think he could have averaged as many as 8 assists a game in the right college situation.) In half-court sets, Simmons was met with the prospects of a high-screen combined with zero off-ball action; how does this best suit a player who is most naturally talented as a passer, above all else? You could even scrap a lot of the high-ball screens, play Benny like a true-point guard and run Blakeney/Hornsby through a maze of screens, combined with some drop-in /back door action from the bigs. None of this will be the case in the NBA, even in the worst case scenario of landing in Philly (Brett Brown is an insanely good coach, despite the situation he's chosen as his maiden voyage into NBA stewardship.) I just don't see how things could even go 1/10th as badly as they went in Baton Rouge, given the quality of oversight he'll receive, regardless of the organization he ends up in.
Contrary to popular opinion, I believe quality passing, not three-point shooting, is likely the most import offensive weapon a team can possess in basketball. This is true at any level, but holds the most water when it comes to the upper-echelon of competition in the NBA. Look at the Warriors; the roster is littered with good to great passers, including a rarity in a true center who is an A-level passer (Bogut is such an underrated cog in the Warriors machine). The real lethal aspect of their long-ball prowess is that it gives them the requisite spacing to carve up teams late in the game with their passing. In San Antonio, passing is valued at premium as well, and has been for a long time, even before it was the essential facet of the historic offense that allowed them to come back and conquer LeBron's Heat in the 2014. The state of basketball in 2016 is so strong because pretty much all the top teams realize that the most important thing is the versatility and resiliency that comes when you play as a team, which is achieved through sharing the ball.
The LeBron/Simmons comparison, while annoying, are spot-on in one regard; both are a once in a generation talent when it comes to moving the rock. SportCenter Top-Tens and viral vines and Instagram highlights might suggest otherwise, but the real winning plays in a basketball game are the sequences where the ball pings around like it's in a pinball machine, to the point where the final recipient has a shot that is, in effect, a 100% efficient. Yes, you need great talents in basketball to win, but you also need team-play, and the two are certainly not mutually exclusive. That's the beauty of Ben Simmons, he fits in that team structure 100%. His bigger issue is maybe that he needs to learn to stand-out.
At this point, I know what you may be thinking, "but he can't shoot! Shooting is so important now-a-days!"
YES, shooting is now undeniably one of the top attributes that you look for in an NBA player, but just because you can't do that at a high-level doesn't mean you can't be a great or extremely effective all-around. If he continues to show a high-level of competency in every area of his game (and improves his decisiveness with the ball in terms of when to shoot or make a move) he likely doesn't even need to become a three-point shooter. The guy is an extremely unique and extremely talented, and if he can just add some semblance of an elbow pull-up or baseline shot, that might be enough. He's got deadly potential as a screener if he can add a 18/19-foot KG shot (above the free throw line) that will allow him to yo-yo his defender between rolls and pops. There's a LOT to work with.
The big issues with his shooting woes are mostly that it limits the amount of time he can spend on the perimeter, both in general and as a P&R ball handler (until he proves them wrong, defenses will always play under and dare him to pull-up). Most of technical issues are fixable problems, though; his shooting motion, top to bottom, is flawed in that he's over reliant on his arms to generate power, the ball tends to be too centered on his body during his shot, his shot is too flat, etc. Shooting is a learned skill, and with the best coaches in the world being in and around the NBA, I have no doubts he'll reach a level of competence that will allow him to do his thing. Maybe not right away, but after a year or two, I'd be surprised if he hasn't added at least a jump-shot tool or two to his belt.
Bottom-line: Simmons has the potential to be a transcendent offensive player in the NBA. While his arms are a bit short (he doesn't get great extension when he goes to the basket which affects his touch and ability to convert up-close) he has all the tools to become a super-efficient point-forward capable of running an offense like a true point guard. His IQ his off the charts, his ball-handling and passing is already at a plus level for a 6-10 guy in the pros (such natural vision and feel with where to ping the ball to next can't be taught, unlike shooting), and he has enough athleticism and ability to dunk on you, which will help keep defenders honest even if the shooting improves as much as we'd hope.
Defensively, he has much more work to do. This is not uncommon of a young player or a number one overall pick, and he definitely has shown enough at the collegiate level to be optimistic about his ability to defend... eventually. Anywhere but Philly, this lack of ability to defend coming in will limit his minutes, certainly in crunch time, and maybe considerably depending on the team. He also starts from some what of a deficit due to his relatively poor length for his height (standing reach of 8-4, which is particularly damning when it comes to shot blocking. Because he won't be able to deter guys up top, he'll need to put on some weight/strength to get fit to battle for position/bang with more "traditional" bigs which he'll have to guard. Due to his incredibly high on-court IQ, it would stand to reason that he would be able to become a plus defender from a positioning and anticipation standpoint rather quickly, and it'll be important that he devotes himself to improving to that end.
First or second overall. As recently as two months ago, Simmons had this spot locked up. Thanks to the abysmal end to the season and recent "character concerns" (his sister has been working at the agency he eventually signed with for over a year, though I don't see how you can fault Simmons for being forced to maneuver a crooked system that forced him to play a year for free), many now view it as a toss-up between Brand Ingram and the Aussie. It likely will come down to fit. Ingram is no sure-shot either, but his performance improved throughout the year (while you can argue Simmons regressed) and he looked good in the tournament (an overrated aspect of scouting, but still somewhat important to certain people) which the Tigers obviously missed all together (that's probably a bigger minus than a great showing in a tournament game could ever be a plus.) As for Simmons, the kid shows a natural feel for the game that few prospects before him have, and that combo of size/vision (both has a ball-handler and a possible recipient out of the pick and roll) has NBA execs drooling. I don't see how you can pass that up. You can find shooting, you can find scoring, you can't find the package that Simmons brings to the table anywhere else. If he can just shore up that jump-shot, he could be a dominant force in the league for years to come