Yeah casting would be a pain in the ass, but the results, obviously, would be stellar. Personally, since I'm not too fond of casting or its cost, I try to avoid it whenever a simpler solution is available. And to be honest I think I have one that would work quite nicely.
You can just make that thing out of a plastic sheet, cut to the shape you want (just the silhouette) then you can build up the bevels with bondo with styrene as a guide, or even simpler would be aves' apoxie sculpt. Since you seem confident in your sculpting skills I'd recommend apoxie sculpt.
You can read up about it here (http://www.avesstudio.com/index.php?...chk=1&Itemid=1
It paints nicely, sands super smooth, and you can leave room to socket a gem into it if you so desire.
If you plan to cast it flexible I'd recommend against it since you can cast it out of plastic then heat it slightly to get a snug fit.
I attached some articles about how I go about sculpting with apoxie. The curved bits and round parts of the sword's handle were apoxie sculpt.