The Kheldian Grace special can go wherever you can fit it. It provides 5% resist to all damage in human form, 13.5% damage in nova form and some extra max HP in dwarf (That will likely be completely wasted because you'll already be at the HP cap).
For essence transfer be aware that it doesn't seem to work in AoEs either, so it would only affect the slotted power if it is single target (At least in my testing).
As far as other specific IOs, I'd suggest looking at some of the builds in this forum, there are a lot of talented people here whose builds can be great starting points when designing your own that fits your own playstyle. Can't go wrong with 5 luck of the gambler global recharge IOs in any build though 🙂