That's a good point. I imagined them being placed a bit behind the frontline where they'd be safe, but still near enough that they'd be close enough for units to rally there in a reasonable amount of time.
I think "missing critical offensive power" is the exact kind of choice that is interesting to make. Do you push forward and grab another mex or two at the cost of your damaged units (and the healthy ones!) or do you send the damaged units back to repair and wait until you can push forward in force?
I'm imagining a choice similar to the feeling you get when you have map control and you're trying to decide when to push. According to a guide I read here once, it's the marginalized player's responsibility to push into you and disrupt your oppressive eco - but it's also a good idea to push the weakened enemy into their small corner of the map to make sure they don't snipe you or tech up too quickly.
Similarly, if this repair idea works out then you'll have the same choice on a smaller scale - do you push and deal more damage to the enemy, slowing them down... Or do you build up your forces for a larger strike?
Also, after a tank battle if both players return to repair then whoever put more mass into repair stations will have their units operational sooner. Meaning they can push sooner while their opponent is still flatfooted. Investing in rapid repair facilities while your opponent invests in... Say, point defence, means you can strike where they're weak more quickly.
EDIT: Also, am noob. Maybe I fell for a noob trap with this idea. Who can say 🤷