I removed them through sql, just as I suspected all upgrades and replacements should be adjusted too, now swordsman doesn't upgrade into anything. Thanks for reminding me sql was an option, xml takes longer.
it is definitely not that easy. You would end up with a broken upgrade path, for example. Swordsmen do not automatically change to upgrading into Musketmen instead just because you deleted MAA. There are possibly some other points of interaction warranting a separate look. To make sure, one first has to go through all the game files and note all instances where those units are mentioned, then decided one by one if they're taken care of by the general delete statement you described or if they require further adjustments.