This thread is a necro, but since it is, let me add...at this point, I say wait and see what the Alchemist changes look like. With all the spells they're adding, there's apt to be a lot more that might be useful to import as Archmage spells. Similarly, the "mix and match" mechanic they've suggested for Alch might fit well thematically with an Archmage too, using their mastery of the weave to splice together spells on the fly. That'd make the tree a little more distinct than just incremental passive bonuses to your existing spellbook.