I am now fantically obsessed with incubi. I'm code-naming them "blenders" because they slice and dice, and the longer you leave them at it stuff just turns to goo.
Awesome models, but fairly limited in your options based on the three poses of metal(yuck) figures. I had to have proper klaivexes (klaivi? klaivii?), and the answer stared me in the face after assembling the hellion pictured below.
It still never ceases to amaze me how far Jes Goodwin hit it out of the park with this model line; it might not be obvious at first glance, but you truly can make just about everything out of the kits.
So to start, the pieces of the incubi models are obviously the biggest limiting factor. Because of how the hands are put onto the klaive and most of the arm is on the body, you don't have much to work with cutting the hands out. The arms/klaive below give you the most arm (and thus are the easiest to work with.) Cut as shown and clean the hands up as much as you can. Drilling out the holes is a very delicate process. I started with a 1/32 dremel bit, then 3/64, then finally 1/16 (wiggling it a little bit for some extra room). I held the arm with a pair of pliers for better grip (and because the metal gets hot when you drill it). If you start with too big a hole it can be very hard to get the hole you want and not drill out the wrong part.....starting small I had no problems with it. Incubi pieces prepped.
On the glaive I cut out the piece on the right of the picture first, where the obvious handle ends. I then matched up the blades and cut the smoother part of the shaft at the base even with the other handle, so as to have them the same length.
The smoother handled one slides in like *butta*; the ridged handle might require some finagling, but with a 1/16 hole wiggled around a bit it shouldn't be too much trouble. Once the knives are securely glued into the hands you don't have a huge range of poses, but there is room to explore. Here's the two I made.