The stack and related issues.
Heyo bringing another issue to the table since your game is broken in so many stupid ways.
Playing Izzet wizards (Historic) Got 600 triggers going onto stack.
This took too long to load while counting towards my timer so this is one issue that you can look into resolving, maybe you can look into reducing/removing vfx and sfx for the stack in order to load it better. (VFX and SFX are worthless to players for the stack, Maybe adding the sound when everything has finished going onto the stack.
While choosing targets either remove the Decline option or make it resolve with no target. The decline option is too random in its targeting and if you are trying to save time you may shock yourself or your creatures enough times to kill yourself/them.
Thus making the decline option and possibly the timed out state to have your spells kill you.
Timed-out should be a temporary state due to players can force opponents into taking lethal damage or being unable to counter certain things.
A better alternative would be creating a temporary timed-out state roughly half the base timer duration.
where it ends upon something new going onto the pre-existing stack, and resetting when phases end and not just when turns end.
To me these don't sound like difficult issues to resolve and ideas to implement for the MTGA development team.