Hi maybe it's not the time to make suggestions because of th future merge but well i wanted to say it anyway
My suggestion is to allow some buildings (barracks, castles and towers) to contain units.
This feature would be very nice in my opinion because for example it would allow you to make traps to your enemy (like leaving "apparently" your camp without protections while in the castle and in the barracks you could put 10 units). The building would have buttons to load and kick all (maybe a max of 5 or 10 units depending from the kind of the units) or just one or two etc. Of course in case of the destruction of the building the units would die if not kicked out before! This feature may seem similar to the one about units carrying other units, even if im my opinion my suggestion would be easier to add since the building dont move.
Greetings.