I remember seeing an Exploiter with a large Samurai on horse inlay in the general area that you talk about. It was a combination of many pieces of MOP and was engraved as well for fine detail. I don't know whether Alembic has a picture of it or not, but it certainly could be done. It was quite large, perhaps 7 across (of course, an Exploiter has more room up there for this sort of thing).
I think it would look best with engraved detail on the body and head, but you really probably do want all the feathers to be separate pieces to show off contrasting texture. In the engraving process, they cut fine lines into the pearl, then fill these cuts with black ink. Way cool. The problem is that it's so cool that you will want to come up with 7 or 8 inlay figures for the fingerboard so Isis has something looking back at her!
For what it's worth, I think with the set of features you're thinking about, it may actually be cheaper to get a Series II than upgrading a Series I (can I possibly have just said cheaper and Series II in the same sentence?). Some of the really big ticket upgrades like LEDs, continuous wood backplates, and the recessed logo are standard in the Series II bass. You pick up more body laminates, master volume, and CVQ controls (which I'm sure you could lose for no extra bucks) for almost nothing (wow, did I just say that almost nothing in a sentence about Series II?).
David Fung