When artists will provide the Mercenary Camp, the mercenary technology will be available from that building, in that way it will be consistent with any other civ with a dedicated building.
The topic is going in a more complex direction involving stuff that probably needs to be redesigned, thus discussed and approved by devs.
- it makes perfectly sense that Maces/Hammers do Crush damage instead of Hack like an Axe or a Sword, still there is an issue with units Crush armor as most unit (if not every) has high crush armor ( i didn't go further thus i don't really know the reason why ). Reducing every organic unit ( infantry, heroes and cavalry, supports and perhaps elephants ) crush armor would result in more room for crush damage dealers like sieges ( which shouldn't be allowed to attack units, for such a system to work ), slingers and eventually Macemen. This is the reason why splitting Macemen damage ( yoddhas too ) from pure Crush to Hack and Crush would be a workaround for the system to work, for the moment. They would be trained and play a role in fights and not just in sneaky sieges, at least.
- it makes sense for Axemen to be Hack damage dealers with a bonus against sieges and wood structures ( which aren't really defined in the current system, but i am talking by abastraction ) and no penalty at all in armor. Soft counters are useful to handle such particular cases.