But replacing lost mainlines is completely different from replacing engineers. If you're issue is that you lost your pioneers and the new ones you built aren't holding up in combat, I mean, that's tough. They aren't supposed to, and my received accuracy suggestion is only meant to help them a little
Biggest reason to want vetted engineers is the repair bonus at vet 2, and they already added a repair speed bonus to the sweeper
I have said this for years, they should also get XP from kills/damage they do with planted mines. It seems the modteam doesn't want this or its not possible because its never made it to a patch
I have never said that pioneers should be potent fighters. But OPs point was that OST pios cannot really get vet after the midgame, which I find to be true. Giving them higher vet bonus helps only if it can be reasonably reached.