Keeping My 5e Players Happy

[S'mon]

I don't think the problem is the TPK, I think the problem is "giving them hint" and resurrecting them with some larger than life NPC. The last problem will be further aggravated when they found out that you were just pulling their leg. If the player characters die: Just. Let. Them. Die. It is not that hard, I promise

I definitely think you harm trust most by raising the dead PCs, negating the consequence
of their actions. Particularly bad when it's an Elminster/Paladine come in to save them.
Conversely it's ok to have the PCs defeated & captured, I've done this a few times - they
can then attempt to escape, be ransomed, etc.

If I were you I'd quickly have it revealed they were raised by the Elder Brain, then give
them a chance to escape its control. And next time there is a TPK, let it ride.

 

[Eejit]

So...when the soul is recalled, the soul knows who, what and when they are being recalled. That soul can either say "Yeah, sure, I'll give it another go!", or "No flippin way am I going back to that craptastic life!". So, basically, they can go back or not...but they know who's pulling the strings. This gives them a chance (as players) to "screw over" the Elder Brain...who would think the PC's are under his "ruse/control/whatever"...allowing the PC's to really stick it to him from the 'inside'. That might make the "you didn't have a choice" thing more palatable.

Precisely. The PHB specifically says out that souls know the name, alignment and god worshipped (if any) of anyone trying to resurrect them, and can choose whether to accept it.