I see that we have different understanding of word "reinforcement".
I understand it as "getting more soldiers" not "more soldiers on frontline while one or more squads will be running to the base and back instead of actually fighting".
You can merge your units, or you can be leading with your Scripts so they'll be dying first...you know, like how you should be.
Not to say Merge isn't useful, it's just no substitute for pulling reinforcements out of thin air like other actual reinforcement methods.