Question/Idea: Garrisoning Buildings?

DISCLAIMER: I haven't played AoE2 in a while. Please take this with a bit of salt, and please be polite.

So, something I recall from the game, was the ability to garrison units into less conventional buildings. Yes, you could garrison them into towers, town centers, and castles...but also into barracks, archery ranges, and stables. docks, and even siege workshops. It puzzled me, as to what this was for. If I remember correctly, units can only fire from TC's, towers, and castles, and can be healed inside TC's and castles...so, what are the others for? Can units be garrisoned into those, to heal, too? Could you theoretically dock a ship into...the dock, to have it repaired passively? One thing I've read is that a building can garrison units as they're produced, to prevent them from being overwhelmed one at a time, and release them all at once, as a kind of defensive measure, but I don't think I've ever seen this happen.

And more to the point, what about outposts? Does anyone ever use those?

So, it made me wonder if something more could be done with this concept. What if these buildings can function similarly to town centers, where garrisoning units (specifically archers & villagers) grants them a small attack. To balance them, they wouldn't be nearly as powerful, and probably wouldn't scale with the number of units garrisoned inside. Maybe a small healing element, as well (tho even slower the TC's). And maybe, they gain an LoS bonus, while garrisoned, too.

Perhaps a civ could be made with this concept? Where most/all of the buildings can be garrisoned for emergency defenses, but cost more wood, as a consequence?

What do you think? Is there more to garrisoned units in non-combat buildings? Is there a multiplayer use for outposts? Would this combat garrison idea be OP? Probably. Let me know! Feedback is appreciated!