Profile of grammar

Currently MP-40 do not work either with flamer since the DPS at range +20 plus minimal nor with sweepers with 3 MP40.

Okay.

It's not the end of the world that pioneer SMGs are weak or useless at the range the flamer is best at. Many units have mismatched weapon ranges, especially when the weapon upgrade is much stronger than the base weapon.

Consider this: Add doctrinal G43s to pioneers, but only in bad doctrines. And the G43s are weak, like Ostruppen LMGs. And you can't get them before building T3/T4.

If you can get both the flamer and sweeper, it makes the flamer much closer to a no-brainer choice. Right now, getting the flamer puts you in debt because you're going to need another squad to sweep mines sooner or later.

What is the difference between "cost-effective" and just regular "effective"? It seems like they are the same but one has cost in front, which is confusing.

What I have known before is that both "cost-effective" and "cost-efficient" mean good for cost, except probably one of them is British English or something like that. If you look them up in the dictionary, it doesn't mention your distinction at all. If you want to say something is effective but expensive you just say it is "effective" or "overpriced" or "effective but overpriced" if you have to be extra clear.

I guess it makes sense that ideally you would have a specific word for this effective-but-costs-too-much concept. But I think trying to bend "cost-effective" to that meaning doesn't work, it's not clear at all. Maybe you should call it "costly-effective", because everyone knows costly is bad. Don't try to call anything "costly-efficient", though, that doesn't make any sense.

Also with your earlier examples, I think sniper is not a good example of a costly-effective unit because it's such a fickle and skill-based unit. If you are great at sniper handling and your sniper survives the whole match getting lots of kills, then it's both very effective and efficient because snipers don't bleed manpower or need repairs. On the other hand, if your sniper kills two men and then walks into an ambush and dies, it's not effective or cost-effective or anything good at all.

A simple example for costly-effective is like, say you're playing as ost against soviets and your opponent is doing some weird joke strategy with lots and lots of quad halftracks and not much else. If you get a panther to counter them, it will work, but it will cost too much because the panzer 4 can do the same thing for much cheaper. So the panzer 4 is more cost-effective and the panther is costly-effective. And panzergrenadiers with panzershrecks aren't even costly-effective, they're just bad because they won't work at all.

TLDR: you should call things "costly-effective" and not "cost-effective".