Arcane could work something like this:
Arcane Power in conjunction with Mana. Both resources constantly regenerate; spells that cost Arcane Power don't cost Mana, and vice-versa. The idea is that you use Arcane Power spells while your Mana regenerates, and Mana spells while your Arcane Power regenerates. There should also be a spell on a long-ish cooldown that allows you to dump your Arcane Power pool into your Mana pool, in order to retain the "dump phase" mechanic of Arcane while sprucing up the "maintain phase" mechanic a little bit.