I believe the fixed turn timer could be too short in many instances, especially when trading is involved. Therefore, I'd like to propose a time bank for players that could be tapped into when more time is required.
I am all for anything that speeds games up.
This doesn’t look like one of those things.
So you want players to not be able to make the best moves they can during each of their turns? Sometimes the moves have to be longer than the default amount. The system should not penalize players for that.
90 seconds is more than enough for even long, complicated turns. At least all that I have encountered so far.