Imo simply resetting is too shallow.Weaver already does this with Unravel, with two charges. Maybe something like make F5 a short 5 second cooldown, and activating it will strengthen the effects of the next skill used? (not counting Auto attacks that is) It's not really meant to be deep or game changing. It's just a small perk for playing core. I don't see Anet adding something complex to elementalists unless they give the profession a complete overhaul.