I think buffing t4 can be done essentially by buffing p4 because the other choices are strong and specialised enough for what they do . So i would give topgunners to the p4 from vet1 with 3/10s of their damage and then max them out at vet 2 .
Another thing that can be done is reducing the price of the tier 3 and 4 upgrades and adding the respective cost to the building instead rewarding some t1/t2--->t4 as alternative to t1/t2--->t3
Your first idea is absolute horrible crap.
Vet 1 tank upgrade is the best upgrade on tanks anyways, crappy mg just doesn't make sense.
Your second idea however I do think is very interesting.
That would make it more doable if you just want the upgrades for flammenwerfer, lmg and Stukas.
The con of this would be that destroying buildings would become (even) more rewarding for the US player.
I think a suppression nade sounds good, but how much of the Assault Nade aesthetic do we want to keep? I.e.
1. One squad member throws one grenade exactly where you click
2. All squad members throw one grenade at another squad (Volks could have a weaker version)
3. All squadmembers throw one grenade at another squad (Volks could have a more expensive version)
But i'm following Tommy on this one.
An ability like number 1 would be better in the sense that it performs more reliable.
I do really think that blitzkrieg needs a reliable tool in the early game. Defensive has tons, Terror has free zeal.
Maybe 'assault' should have a passive ability besides w/e grenade type it receives.
BUT
/joke
12ock
Zylfi17
Relic Entertainment
보드카 중대 
Heartless Jäger 
