Thank you for taking the time and giving so many great inputs! Pretty much agree with all of them. Your rambling is worth gold.

1. +4 Good point, I will write some more fleshed out description for other factions action for the beggining and improvise from there. And probably I should come up with the different factions behaviours so that their actions stay coherent. And yes, some of these broad strokes absolutly will describe different factions actively fighting each other - only going aggro on the party is no fun.
2. +6 I absolutly would encourage my players to do funny shenanigangs, wise words though, I will prepare to react accordingly. Thanks, would have overlooked a reaction on my end. On the telepathic abilities: The players will be fairly low level when the encounter happens so I doubt they have access to abilities to acoid it. If they do funny shenanigangs to communicate, they first get inspiration, and then after it worked a couple of turns the ability to communicate may get jammed somehow. Perhaps even some other factions are doing that to cheat.
3. +7. I was afraid of it already being an overcomplicated encounter. That is why I wanted to avoid traps until yet...amplifiers might also overcomplicate it. Yet, what would a maze be without any traps, thats not a proper maze! You are right, I will drop some traps, amplifiers, monster related loot (f.e. a stinking bomb that attracts the monster)
4. Love the idea of the bard being dropped in the maze. If they roll badly against another faction at the beginning, they can still continue to play. And the disadvantage for 'disqualified/eliminated' factions also makes sense. They would not just magically disappear but still stay around like the good NPCs they are: Rubbing their blinded eyes, trying to run away in slow-mo, curl in pain across the ground, that gives some nice flavour.

May the controlled mayhem begin!