The hospital,heal station,medics and all that has already been suggested and it's not going to be implemented.Search the forum threads you'll find plenty discussions about this.
The units already heals at day change for free unless if you use gold.Now an extra building must be constructed which uses extra resources to heal units.Units will have to leave the front line and travel back to a hospital,heal there and travel back to the front, where units can be placed near the front out of the way and heal at every day change.
