I'm currently doing this. I got everything I actually wanted from GNW treasure (Edo Sasori to 4*, Kushimaru and Jinpachi), so now I'm only drawing from Edo treasure for the extra Gengetsu frags I can get (along with getting them from the Exchange section). It'll take a while though but if you don't actually need anything else, I'd say go for it.

Wait for other people's opinions though.