Is your goal to mechanically handle the upgrading of the weapons, or to just track the evolution of the weapons somewhere? Honestly, in the interest of simplicity, I'd probably go with something like a journal entry for the ancestral weapons, with a page of clickable rollable tables for any rolls they'd need to do (or for any thematic info, like a wiki) and then write (or ask players to write) a cool thematic blurb for each "level" up of the weapon if that's something they're interested in having/doing.
I'm not aware of any modules that handle this automatically, but I think it's not something I'd see as worth building out.
If you really want to go mechanical with it, you could do an actor sheet and build all the different "level up" stuff as features, put it all in a compendium, and then have players select/drop in features from that compendium... the obvious downside is that all still has to be manually updated when the day is done. Then again, there are worse tasks than getting to bump your weapon up to +2 :).