I was thinking about this based on the expectations thread, that is actually quite a lot. Some of these are debatable, but I do think most of them he would based on team need and who they currently start.
Cavs: Yes
Jr Smith at 32 is on the decline and defense has far and away been the biggest issue for the Cavs this season. They have plenty of offensive firepower with Lebron, Love and Irving and Smart would help cover for Irving's weakness on defense and allow Lebron to expend less effort on defense (this honestly seems like a no brainer)
Bucks : Yes
While Snell is a better shooter, I think that Smart's overall defensive game more than offsets that and think he would start. However, this is debatable.
Toronto: No.
He clearly would not start over Demar
Warriors: No
He clearly would not start over Klay
Blazers: No he clearly would not start over Mccollum
Memphis: Yes
He is clearly a better player than 40 year old Vince Carter or James Ennis. They would a much better team with Smart alongside Conley and Gasol in the starting lineup.
Utah: Yes
I think he is a much more complete player than Ingles and would slot along the offensive firepower of Hill and Hayward.
Spurs: Yes
Green has quietly not improved at all since his games in the finals years back and shooting 37 and 39% from the field the last two years is not enough to make up for the difference in defense and playmaking between the two.
Bulls: No (but maybe should)
It would probably actually make sense for them to not start Butler and Wade together given Wade's injuries and edge, but they would probably never do it over egos.
Wizards: No
He is not as good as Beal.
Atlanta: Maybe, probably not
Hardaway has certainly had a great second half of the season and Smart would probably fit worse alongside schroeder. That being said, I do think Smart is the better player and that would be a fearsome defense backcourt.
Celtics: No
Obviously
Pacers: Yes
He is a better player than CJ Miles and would help cover for the defensive weakness of Teague
Clippers: Probably not
With Blake out they need the offensive firepower Reddick offers, but perhaps as next season the aging Reddick may slot in behind Smart and Crawford would further see his role reduced as he approaches 40 years old.
I know I am forgetting a few playoff teams but am running out of time and will come back and edit this.
So you make a case that Smart could start for at least 6 of the teams in the playoffs, including the defending champions, and maybe half of them. I think looking at it throw that lens maybe may make some appreciate Smart more.
I disagree about the Cavs. If they wanted more defense and less offense at the SG position, they would be starting Shumpert over Smith. Plus, I don't think they could justify bringing Smith off the bench after giving him that 4/57 deal.
I also disagree about the Bucks. That team is strapped for shooting (less so since Middleton returned, but still in need), and having Snell spreading the floor is more valuable than Smart's added defense.
Agreed on Toronto, Golden State, and the Blazers.
Memphis he would definitely start right now. He would give the team a similar dynamic to when Tony Allen is healthy. If Allen were healthy right now, then it's debatable, but TA would likely start due to his experience, both with the team/lineup and in general.
Jazz I can't see him starting on, but I also can't see Ingles starting on that team so who knows. I'm not sure whether Smart would replace Ingles, but given that they are already a great defensive team I think they'd prefer Ingles' shooting.
He probably wouldn't start for the Spurs given Green's 38% 3p shooting. Green's struggling from the field this year, but he's still a very good 3 and D player and pretty much perfect for his role on that team.
Smart would start for the Bulls at PG right now, no questions asked. MCW, Grant, and Canaan are undoubtedly worse than him (Canaan is a better shooter, but Smart blows him away in every other part of the game). With a healthy Rondo, though, Smart comes off the bench.
Agreed on the Wizards.
For the Hawks, I don't think he would start. With an inside guy like Dwight you need to spread the floor, and a little added defense means less when there's someone there to clean up a perimeter defender's mistakes. It's possible he starts while playing a guard-heavy team like Washington, though, since he's the way better defender.
Agreed on the Pacers. Miles is the better shooter, but that team can already stretch the floor so having a great defender to cover for Teague would be a huge help, especially in a series against an elite PG like Irving.
Clippers he wouldn't start for. that team needs outside shooting, not another great guard defender. When Chris Paul was out he might have, though.
Teams you didn't mention (yet):
Rockets: no, Beverly is the much better shooter while also being a very good defender. This is a spot where AB would definitely start, but not Smart.
OKC: Smart would start over Roberson in a series against a team without a star scoring SF like the Rockets. Smart would be able to cover Harden when needed and would be able to cover Ariza when it wasn't needed. And say what you will about Smart, but his offense isn't so terrible that teams play "Hack-A-Smart" (and if they did for some reason, he's god enough to actually hit his FTs)
So I figure he definitely starts on 4/16 playoff teams right now, and is a maybe on 2 others (but keep in mind that 2 of the teams he definitely starts on, Bulls and Memphis, are due to injuries). Not bad for our current 6th man