I've looked at their signer code, that part is easy, basically already done in Armory since it copies the BCH replay protection as is. Couldn't find anything about their new address format or any of their other changes, so I'd have to actually crawl through their changeset to get this done, and well... what's in it for me? Realistically, BTG is a 1% bump for maybe a week of work, mostly spent trying to figure wtf they changed in there, with the added risk of fiddling with signer and address code?

Bottom line, the reward doesn't justify the risk.