Yeah, that a good idea to add tags "ACE Compatible". ACE is a standard now and many people just treat it like ArmA patch 1.96 . But ACE lacks some things and some other things have better alternative... So adding tag would be great. And i suggest having 2 different tags:
ACE - Compatible - 100% working, using all ACE feature for that type of addon.
ACE - Working - Just working without errors and other problems.