This is a great post. Bernardoni-esque, if you will.
Fans are under appreciating this dynamic. The Celtics can not keep "running it back". It's easy to just roll your eyes and say "It's just Wyc's money" but the reality is that the *repeater* tax is what is a killer. The owners will be spending MULTIPLES of whatever they would be over the tax line, if they are in fact over the line for multiple years. None of us, no matter how rich, are stupid enough to consent to such a thing for a non-contending team.
I really sense this is a pivotal offseason for the team. I think Ainge is going to seek to do one of the following to simultaneously clean up the future salary landscape and improve the team:
1) trade Kemba's last two years (helps that he's been playing like an all-star again of late) for a legit super-star to pair with Tatum and Brown. Let Fournier walk, or try and sign him and be over the tax if you believe you've vaulted yourself into contention.
2) offload Kemba's last two years for picks, if you can pull it off, to be used down the line to trade for a superstar. You'll be under the tax with contracts you can still aggregate up to a max contract (Smart/Fournier/Thompson/etc.)
3) try to sign and trade Fournier for anything of value that can ultimately be used in the future to trade for a superstar.
4) trade Brown plus another contract (again, like Smart/Thompson/Fournier) plus whatever additional draft capital for a superstar. Again, go ahead and be over the tax; you'll be a contender.
5) trade younger guys and/or role players on the roster for future draft capital, again, with the idea of trading for a superstar.
In my opinion, the simplest thing to do is to trade Kemba into someone else's cap space. I don't think you'll need to attach picks to get this done; there will be a team out there who's interested in Kemba. Establish your identity as a switch-everything, gritty defensive team led by the Jays, and keep your options and your assets open for the next disgruntled superstar a la what the Nets pulled off with Harden this year.