Well, back in days there was no way to make 2 procs to live together on 1 toon. Then LE come and there was major overhaul of "how procs are gonna work".
Now we can have many procs at once (2x LE, 2x agent procs, weapon proc or two, ring proc, helmet proc, etc,etc,etc).
So - FC showed that they can fix issues of such level.
So here goes suggestion:
1. Separate "use item" queue from "perk queue". So you can use stims/trimmers/other usable items while perking.
Example: you got stunned, but can't use free movement stim cause "wait for current action execution" due to perk you launched pre-stun.
Example2: Long perks like engineer' Demolitions line means you can't do nothing during perk execution, no trimming pets, no stimming self in case some1 hit you.
2. Separate nano execution queues. Make one for "player" nanos and one for "automagic" ones like aura ticks/proc start/etc. And for "automagic" one - remove "locking" of other actions when player have it active. So you can swap items/cast nanos/reload/use items even if your proc fired off/aura on keeper ticked/etc.
Example: Team up as NT with 2 keepers/crat/trader/soldier. Try to nuke once they all finished buffing.
Example2: Get flags and try to cast long nano near big blob of buffing up players. 99% that your nanocast will be interrupted.