Inspired by this comment on MaRo's blog, this was designed to be a Legend who could work equally well as Commander of a 2-colour, 3-colour, or 4-colour EDH deck. It's funny how the red-white effects on Lightning Helix and Martial Glory (earlier Cromat) match monocoloured effects in Essence Drain and Giant Growth.

The "A or B" cost template is unusual, but was seen before on the Crystal Shard cycle. Interestingly those could now be errataed to use monocoloured hybrid technology like , but the costs I want here can't so easily be hybridised. I don't want you to be able to drain life for or : it's either or , okay?

Oh hey, this is very cute. It is too bad hybrid doesn't work, because that would make things a bit more succinct, but as you point out, there is a precedent for costs like this.
Isn't Agrus Kos dead, though? :-(

The Golgari got to him. (Not really, but for this particular implementation.) Make it a Lich Soldier and you're good to go.

Ha! Yeah, I guess I should have come up with a different name.

Given that I have to pay RW to cast him, why would I want to spend BB or GG to use his abilities?

Good question. Perhaps this should be an artifact, or an equipment. Or a blue creature.