So I've tried this and it was harder than expected and I'm not sure 100 percent I like the results as there were a couple of big issues I encountered when making them.
There are cables, grenades, buttons and ammo pouches all over the models which need to be removed. This took far longer than I expected it to.
The arms weren't easily compatible. I had to remove shields off of arms so I could then glue them on. Also the arms are different widths between the kits. Again this took a long time to sort out.
The two kits have different head joints. The witch elf heads lack a neck which meant each head had to have a blob of green stuff to hold the head up high enough to look normal. Don't even get me started on the hair, I gave up and used the masks.
Finally the wyches are slightly smaller on the battlefield. They aren't jumping off of rocks or doing other similar poses and this makes them stand out as different which combined with the masks meant they looked less like witch elves than I wanted.
I saved money doing the conversion but I probably spent 5 times longer making a unit I'm not super happy with, doesn't fit in with the rest of my army and will probably be replacing in the summer.
