The heal/damage over time thing is a big change from the way the BS works now, but it is interesting enough to give it a shot. Making the system ready for a fully customizable set of skills would be too much work though. I think I could start by adding one or more element to tag skills that would deal damage or heal over time instead of at the moment they are used. These skills would use the same damage/heal formulae of ordinary skills, with elemental correction and all that stuff, but the effect would be spread over multiple turns. I can foresee a lot of work here.
Let's say I like the idea but I don't know when I will do it.

@polo12
yeah, that bug has been pointed out before, change that line into