It's entirely possible that Sullinger down low could be a major handful for the heat. Sullinger shot a very high % the last two years for Ohio State, all while being the go-to option and putting up lots of shots.
Sullinger had a very untimely off-game against the length of Kansas, but I think OSU's 2nd scoring option was injured and out of the game, and Sullinger was forcing the issue. It wasn't just the length he was facing, it was that Sullinger was trying to do too much as well.
Right now Sullinger is working on expanding his moves and combinations of moves. With any luck, by the time the playoffs come around Sullinger will be well equipped to repeatedly attack Bosh and Lebron down low, even if it means leaning into them before fading away with jumpers or jump hooks. With a couple nice combinations of moves, Sullinger could be a foul magnet against Bosh and James, assuming the Stern Gang wants to play by the rules, lol.
If Sullinger isn't an expert at drawing fouls against NBA length by the playoffs, expect him to develop that ability soon in his career.
Sullinger would manhandle Bosh on the boards, and establish position down low at will on offense.
If Sullinger shows enough tricks up his sleeve, he could leave the Heat scrambling for solutions as much as Doc scrambles for solutions to James at 4.
KG, Wilcox, Sullinger, and possibly Melo. Some combination of those guys will be ready to step up to the challenge at 5. Even Melo could be an interesting look against Bosh if he can develop a couple nice post moves and counter moves. If Melo can learn to draw the foul (he already knows how to draw the charge), he could definitely be a force in the playoffs or before.