I've made the following merges:
wheezy -> raspbian-wheezy
jessie -> raspbian-jessie
stretch -> raspbian-stretch
All with synonyms so they don't reappear.
As for the lite forms, I suppose they can follow the same pattern -- since there is still a plain raspbian there might as well be a raspbian-lite, then a jessie-lite, etc.
Realistically, most ...
Well, technically wlan is a broader term than Wi-Fi which just happens to be a brand name... and, uhm well, describing the (by far) most widely adopted standard.
Interestingly Electronics.SE does not even have a wlan. Unix&Linux does not synonymize wlan with wifi - though they have no tag definition for wlan either, use it only sparringly, and often ...
I'm not that familiar with the process, but would it be possible to change the old XBMC tags to XMBC-depreciated (or something) and have all tags going forward be XBMC?
Personally, I would prefer to see the old XBMC tags under their own name. New names often bring a whole host of changes, and things that were true with XBMC, might not be the same with Kodi....