In itself it would be great, but the developers would be overwhelmed with it. Consider all the killer powers that are already not working as intended.

Behaviour has had trouble implementing just one new killer (wesker). You are now suggesting they add 33 brand new unique active powers to the game? Even if this idea was good, it could never plausibly happen. It would take ages to implement, balancing would be a nightmare and there would be bugs galore.

Wesker is a buggy mess right now. I am doing well with him to but he has some frustrating bugs (I grab and let go of survivors very often).

Balance is a very valid argument when your adding 33 new powers into the game (that is more effort needed than if they were to add the entire killer roster to the game again). Not to mention bugs and stuff like that which again you saw how buggy twins was on their release, the exact same would likely happen with this.

You cant remove the multible Survivor selection for Trial, because it would be really bad for beginners. If they just lvl dwight and than they cant play dwight

The problem in this idea is, that this Survivor powers would work like a perk. Means that you as the killer have to deal with 20 Perks and you have 5, if you count your own power as a perk.

Behaviour cant just simply fix these issues, have you seen how long it takes them to implement changes and bug fixes?

Don't use the kill switch as an argument btw. It is super inconsistent (Oni dropped way more blood than he should and they fixed it like 2 months later without kill switching him which they arguably should have for sure).

Also they would have to add the majority at once at the very least, because if they just added say one surv with powers then every single person on earth would play that one survivor since they would be objectively the best one to play.

Why the devs will never do this and why its a terrible idea

1. . A meta will be formed. all players will pick Everyone will pick the same character because there will invariably be one character more powerful then the rest. Not only will this make the game less visually interesting because every match will have say 4 Megs, this will create further stagnation that the devs are trying to avoid. Maybe they can do what other games do, only allow one character rper match. You think players giving up during a match is bad, wait until they start quitting when their main is taken before the match starts. Or if you put in a penalty, killing themselves on hook 3 seconds in.
2. It will create massive unbalance. Now not only you have to avoid unbalance of a perk base, and unbalance when combined with other perks, but now you have to balance perks for all survivors? They can't do it. They don't have the vison for it, and to do it would take years.
3. killers would go mental. A large portion of the killer main base goes mental any time survivors get any buff, even the most modest of compensations. You think we would not see hundreds of forums posts of outrage when survivors get 30+ buffs? There would be outrage everywhere and killers threatening to quit the game.
4. They would lose money. Behaviour makes so much money form cosmetics. People will pick a main and never deviate. So they won't buy cosmetics for other characters. "But people already do that?" yes, and there is no reason to, is entirely subjective, and already a lot of people think like that. wait until people have a reason, cosmetic sales will crash.

Its bad for the game, and bad for business. They will likely never do it.

The idea is unworkable and it is never going to be implemented ever.

Yes but you cant lvl all of them at once. As a beginner maybe you what to lvl dwight first on 40 and than other Survivors means the newbie want to play dwight more than the others, because dwight is the only on he/she have lvled at the moment