A few things wrong about that. First why is 3v3 and 4v4 even a consideration? COH is not balanced for those modes, it cannot be done. Making 1v1 more balanced will trickle up, but it can never be as balanced because team games have unit combinations that aren't possible in 1v1. For example if Sturmtiger + Jagdtiger is a really OP combo, that issue only exist in team games. Then if you nerf those because of 4v4 casuals they become underpowered in 1v1.
More people play team modes than play 1v1. "Why is 3v3 and 4v4 even a consideration?" is as much a useless question as "why does CoH have skirmish AI or a campaign?"
The issue with balance in 4v4, 3v3, and to a lesser extent 2v2 is because CoH2 has been designed around 1v1. This isn't in itself an issue, as 1v1 balance can definitely scale well into team games. The problem is that Relic gave little to no thought as to how mechanics scaled (Old Opel Blitz, Caches etc.). Fixing the way resource income scales in team games and adjusting the maps would make 3v3 and 4v4 much more like 1v1.
And just because you start with veterancy does not make it ok to lose units. It makes it a little less painful, but you still lose the manpower, still lose the munitions if you buy another weapon upgrade, you might lose some map control, and you still feed vet to other guy when you lost the unit. Plus the process of earning vet has gotten easier than it used to be, vet is now a participation trophy for getting in combat rather than something you earn by getting kills. Receive damage earn experience, lel. Get a couple vehicles hits with infantry AT earn easy vet, lel.
Having bought veterancy matched against earned veterancy means the veterancy system doesn't scale well into larger game-modes, which clearly doesn't concern you, but is not something Relic is likely to be interested in given more play team games than 1v1.
The problem with veterancy via kills is that it favours bigger, tougher units (i.e., units that don't need veterancy).