I've thought about a similar approach myself and I agree it is a more wholesome solution to fix T1's AT problem. The PTRS upgrade for Penals always felt a bit shoehorned into T1.
Balance wise, it would have a much greater impact than improving the PTRS upgrade on Penals. T1 would have access to more sandbags (and other utility) from the PTRS Conscripts. Penals would be able to focus fully on their AI role. Giving AT satchels to all Penals would also be a big (maybe unnecessary) change. T1 would be played very differently from now.
It's an interesting idea that would definitely be worth testing, but it would require further finetuning like Vipper said.
It leaves Tank Hunters PTRS upgrade in question.