Yeah the relief infantry and conscription abilities are absolutely worthless trash. They've both been nerfed to the ground.
I have to agree.
While the original idea was nice, it just does not work that well in the game. If you max it out, you exchange MUN for MP at a rate of 1:~4, which is usually a good deal. But often you do not want two additional infantry units, because they will just block your build. And since loosing units is a big deal, you cannot sacrifice units the already vetted units (for example in order to surprise your opponent with a quick second wave).
I suggest reworking this ability (if possible) to reduce reinforcement costs. For example, if we say in a bigger fight usually 10-15 infantry models die (4-5 Gren/Pio squads lose 3 models each plus maybe some support unit models) then the reinforcement cost would be a bit more than 300 MP. If the ability would give a 50% cost reduction (just an example) it would save ~150 MP which would suggest a price of about 35-50 MUN.
Make the ability last for a minute or so, that's enough to limit it to usually one fight only per squad. Adjust the CD accordingly, so that it cannot be spammed.
Advantages: You can activate it when you need it and don't need to remember to click the button when you get overrun. Unit preservation is still promoted, you don't get squads that you might not need. It helps you from the mid game onwards to save some MP and could help bleed heavy factions like OST to reduce that.
There are side effects from this (for example it would not work that well with Osttruppen or Conscript builds) and a lot of other stuff, but all in all it could be a nice idea. As of now, the ability is not used anyways, so unless it goes super OP, there's nothing to lose.