I can't tell what you're going for here.
MP is already, for all intents and purposes, DRK's primary job gauge. It has the most generators and is spent from the earliest level of any gauge. As such...
- Why would it help to switch our MP-spender(-and-Darkside-generator) into a Darkside- or Blood-spender?
- Likewise, how does it help to swap the level at which we get our 3.33-charge, frequently-available AoE oGCD (Flood) with our single-charge 60s-CD AoE oGCD that interacts with no other manipulable resource (Abyssal Drain)?
If this is related at all to the suggested Edge change, again, I'm not seeing the benefit. Making Edge part of a Blood-spending combo just replaces what are currently two actions (our offensive ST MP spender and, separately, our ST Blood spender) with a single action that just takes 2 button-presses to complete.
Why would Enmity combos "have to come back," though?