So someone who has lots of resources and carefully managed his units through out the game should not be able to get stronger because his enemy who lost the 3rd Sqaud in a row can't catch up any more?
How can anyone see it as good game design that people who haven't lost a single unit in the whole game are forced to send one squad on a suicide mission for no reason (or keep mulitple squads at 25%) just so they can get another unit? It is wasting a unit, it is giving the enemy free EXP, sometimes it might even be giving the enemy free Stuff like LMGs
Like I said. Where is the probelm with people not being able to catch up after playing bad? Also this is not entirely true. Player 1 decides to go for Another Tank despite already having 99 pop cap, so Player 2 will get more ressources (assuming he is holding as much points as Player 1) during this time and thus can catch slightly up
People wouldn't be able to amass 200 pop cap armies anyways because by that time the Ressource Drain would become too high so it isn't that much of a change from CoH2 anyways
That's quite exaggerated. If there is such a huge skill difference that one player loses nothing and the other gets wiped regularly, also the current system will punish that.
The point is that a game that is so heavily based on RNG like CoH needs to have come back mechanics, because some bad engagements are not due to your own fault, but just bad luck.
To your original point though: Where exactly you want to draw that line between allowing a come back and rewarding good play is quite subjective. The 100 POP cap seemed to generally work quite well for CoH2. Allowing higher pop must come as you suggested with higher than linear cost, since these additional units will always be tanks that do not bleed any resources. I think you could implement it with proper testing, but on the other hand there is also not much need to do so if the 100 POP cap works decently well.
For custom games, I'd like an option to remove pop cap and maybe even select different types of cost-scaling. For multiplayer? Maybe rather not, not sure if it is worth the additional effort if the 100 POP cap system could just be tuned instead.