Man what a tremendous idea that can never happen because:
1. You need to renounce Kyrie just to open any cap space so can't resign him using Bird rights. And even in your scenario, you aren't opening two max slots. Off the top of my head(salary in millions):
Hayward $32.7
Smart $12.5
Tatum $7.8
Brown $6.5
Yabu $3.1
Semi $1.6
Timelord $1.9
GWilliams $1.9
Langford $2.9
3 empty roster slots @ $2.7
My math has the team at $73.6 million or $35.4 million in cap space assuming everyone is renounced.
2. The Celtics aren't salary dumping Brown in any way. Yes you salary dump Yabu and Baynes. You don't salary dump a possibly emerging star still on a rookie deal.
3. Salary dumping Brown and Yabu only opens $7.8 million because they are replaced by empty roster slot cap hold of $900,000. Doing that awful trade only opens up $43.2 million.
3. You need to renounce everyone for cap space meaning you can not re-sign Morris and Irving using Bird rights.
4. Once you use salary cap space you lose the ability to use the regular MLE, the tax payer MLE and the BAE. All you have left is the Room Exception($4.7 million) and vet minimum contracts to sign other players.
5. Neither Durant nor Irving are eligible for super max contracts from the Celtics. Durant can get one from GSW only and Kyrie isn't eligible for one.
So in other words, your whole scenario can not and will not happen.
I suggest reading and referencing this site to understand more about the salary cap, how it works, how trades work and a lot more. It will help you to not waste so much effort on an idea just to be told none of it can happen:
www.cbafaq.com