Smart is playing 32 mpg here, he wouldn't be playing much more than that (if at all) in Philly, and while he might get an extra shot here or there, his percentage isn't going to magically increase playing on a worse team, so I'd say he will still be in the 10-12 range he is at right now.
Similarly, I don't foresee Rozier or Brown getting many more minutes than already do as I believe Rodriguez and Covington would still start and play around the minutes they do. I also think Bayless would be ahead of Rozier on the depth chart so when he is back Rozier would get even less minutes. So let's say Brown 6-8 like now and Rozier 5-7 also like now.
It's a cute thought experiment, but it's flawed. It's based on the premise that our team is so great that our bench players would flourish on a bad team. I get it. I understand why this thread was created. If we considered the hypothetical realistically, though, it's not how most here are flippantly imagining.
I should clarify that I'm approaching this from the perspective of what a fully healthy Philly team looks like. I'm not talking about Philly the past two years that was literally starting D-League players and intentionally trying to lose games. Those days are essentially over. While they have struggled, they have some competent players on that team now. I'm looking at this from the perspective of a team built around the offense of their bigs (Embiid and Okafor), with Ben Simmons projected to be their primary ball-handler. That team requires shooting to spread the floor. It's why a defense-first SF like Convington is potentially on the verge of losing his minutes to a flaming hot shooter Nik Stauskas (
http://www.phillymag.com/news/2016/11/21/should-nik-stauskas-be-starting-over-robert-covington/ )...
We're not talking about a team that was starting unknown undrafted scrubs. This is a team that has some decent vets now between Ilysolva, Gerald Henderson, Sergio Rodriguez and eventually Jerryd Bayless (coming off a great shooting season). What that team needs, Marcus does not provide. He's shooting historically bad percentages. While his defense is great, a team with dominant low-post players and a ball-dominating forward who can't shoot (Simmons) does not need a guard with historically bad offense.
So, I'd say Marcus would come off the bench in Philly and average less than the 32mpg he's been averaging here. Marcus has the luxury of playing alongside several players who can shoot. In Philly, he's a liability.
Jaylen's efficiency is high because he's picking and choosing his spots and only taking wide open attempts, dunks and drives. His FG% is really solid at the moment 46%/35%/63%... that wouldn't happen on Philly. He's proven in College, Summerleague and Pre-season that he's a sub 40% shooter and he'd struggle to be effective in that lineup. Also, playing in Philly would likely stunt his development ... as he's a decent prospect with a theoretical high ceiling, because he's playing in this winning culture with a quality coaching staff and excellent players like Jae Crowder to go head to head with daily. Stick him on a team like the Kings, Philly, Suns, etc and Jaylen's ceiling drops dramatically.
The only player I think could actually contribute off the bat is Terry Rozier. Right now he's buried behind several guards (Bradley, Thomas, Smart). He's shooting 41% and a very encouraging 45% from three. That's the kind of shooting Philly needs. Before the Detroit dud, he had a game where he posted career highs in points (11), rebounds (7) and assists (5). It's ridiculous to imagine him suddenly averaging 15 and 8 on another team, but I will say that if he could continue his effective shooting he'd quickly find a role. He'd start as being behind Rodriguez and Bayless on the depth chart, but could find himself with a quicker path to the starting lineup if he played well enough. If your expectations is that he'd immediately start, you're wrong. He'd have to earn his spot. He's getting 19.5 minutes in Boston. MAYBE he'd get that right away on Philly. He'd probably take a big chunk of TJ McConnell's minutes (currently averaging 19.8 off the bench). But keep in mind that McConnell is only averaging 19.8 because Bayless hasn't played a game yet. Bayless is projected to start for them. Beyond that it just depends how he fit alongside the rest of those players.
The opposite is just as likely to happen. There are players on Philly who would fit much better in this system with this supporting cast. Okafor and Noel, for instance, are two players I think could post better stats in Boston than either posts on that Philly team. I'm not alone in believing this. Respectable NBA analysts have said as much... stick Noel on a team with competent teammates and he'll probably look much better.