Fundamentally, I dont think timers fit this structure of a game. They are either forgiving to the point of being irrelevant, or get in the way of fun. “Find help before you become mindflayer” is a fun scenario to think about, but not a great fit for stating cRPG with a big focus on exploration.
As it was pointed before, BG3 doesn’t even have narrative ticking bomb. Characters think so initially, but it is established later on that the tadpole is dormant.
So I think it is all well to theorycraft a hypothetical game that would use tadpoles and timers, or think how BG3 could have less convoluted story hook, but none of it has much relation to game as is - which won’t be heavily redesigned nor rewritten at this point.
This sort of idea is suited to a challenge mode. We all know by now that players would like more custom and/or challenge run variants. There's various mods that fill such niches at the moment.
The consequences don't have to be dire. Some story events could just have a timer (Grove gets run over by goblins, Isobel is kidnapped). It *could* be dire, but not related to the tadpole. Hell, you're travelling with a living bomb. It could also be tied to the tadpole for once, in this challenge mode only.
OP did not ask to completely and fundamentally change the base game. It's just a suggestion for an optional scenario.
