Just won't get between Katitof and you,
You are not he has not interest in providing any feedback since he does not play the game and just likes to troll.
but T1 Penals with Flamer were in a completely different time frame. Yeah, they were an issue. But thats absolutely not comparable or scaleable: Different factions and early vs late...
My suggestion test flamer Ro. e in game.
As for penal comparison it non constructive but if you want to make it:
Ro. e:
cost only 210 and are dirty cheap to reinforce
start with 0.9 size and up with 0.59 and armor on top of that
Get a flamer and 2 LMG
Have AT grenades
so I suspect they will be a problem also.
Still don't like your suggestion of Anvil Engineers. That way you have IS clones (LMG+Enfields) with additional engineer options. Wow, that is a lackluster. Why not making them a unique fighting unit?
The problem with Vickers K is that it does not work well with smg so giving them enfields is actually a buff.
In addition since the have superior repair speed they should designed to be used less aggressively, the upgrade is optional anyway.