the flamethrower isn't the problem, the svt 40 is the problem. The flamethrower can ignore the defensive on
Just as a word of caution; if you made them so effective that they represented a clear advantage over Cons, then one would expect the meta to shift so that T1 is standard and Cons never get built. This is especially likely if they get infantry AT.
We should never be trying to make Penals so effective that they automatically overshadow Cons. At the moment the only real issue that exists with Penals is they are under-used. And that problem is not necessarily going to be solved by taking them a better unit to build in terms of effectiveness for cost.
Frex, if Penals were both buffed and priced to the equivalent of Obers, you might well see more of them. Back-teching to T1 mid-game when you can afford to start fielding elite infantry might easily be seen as worth it.
I'm not offering that as a serious suggestion, only pointing out that bufff/debuff is not really the issue at hand.