PTRS is not a weapon upgrade, it's a mediocre sidegrade.
That comment is simply beneath you, you post are usually are much higher quality than that. (I suggest you leave semantic games to another user)
There is nothing wrong with AI DPS of Penals they have good DPS at all ranges.
Saying all these things are just a problem of the tier building and not Penals themselves is true but I can't build Penals in other tier buildings so what is the point? Penals do have these drawbacks and there is no denying that. Only way to solve them is by going for a doctrine with dhsk/m42. It's simply not possible to get 3 Penals + T2 + Zis/Maxim as you will never have enough MP unless it's a complete noob stomp.
The flaw in you logic it that you expect Penals to carry all faction on their shoulders they can not and the should not. Else you would simply have Penal blobs running around the same way you had VG shcreck blobs.
Penal are cost effective unit with no drawbacks, any and all problems with them are related to the design of T1.