None of that will discourage pvp. If the spy can die while he is in stealth then that is a good thing. If he has to run the risk of dying by his own hand then that too is a good thing. It will stop all these stealth as soon as you get hit wannabe spies.

My first char was a spy. I took him to op fights when there were only a handful of good spies playing NC. I went to fights before stealth and I died as much as I killed. It was a better time back then.

It wouldnt discourage pvp it would make the spy think about his fight and whether he could beat the opponent or not, not when would he need to hit the stealth and get the fuck out of the way before the other guy had a chance to retaliate.

P.s healing rate? huh? What class can heal faster than a spy? (besides a ppu) Spy can use the heal tool or the heal spell just the same as the PE. Tank can only use tools. Healing rates are pretty similar across the board tbh. Damage output whilst not receiving too much by return is where the spy wins. He wins a war of attrition more or less every time vs another class. Because of his stealth.

This is why the stealth needs to have a penalty. A radiation stack OR your idea of no heal while in stealth are both valid ideas. The spy needs a penalty of some form on his stealth. It should not be used to carry on the fight if the other class doesnt have it. That is what makes it OP.

In reference to your original question no not every class has a way to combat stealth. Yes tanks have another gun they can bring, PPUs have TSS yeah also true. APU has a barrel which might catch the spy if he is incredibly stupid. HC Pe might catch him with a fire stack sure. So ok HC and PPU can find the spy - you mostly find those at op fights. So that means you "rely" on those guys to catch the spy out.

No this is not a valid solution. Pistol PE has no way to fight the stealth (No DoT from the Wyatt Earp any more), nor do APUs (No DoT any more from anything visible - Fire Apoc is all burst now I believe). Damage boost is not a viable option as it is too slow for the PE to cast and only the holy one is any good for lighting them up due to RoF and range.

Rifle PE has nothing to fight it that I can honestly think of. Other spies have nothing to fight stealth barring their own stealth so no I do not know what other stuff you can use.

You cannot balance pvp based on situations either. It has to be balanced 1v1 first in my mind. If you try to start to think of every single combination of chars and balance them all then you will be here into the next decade tbh.