well, to maximize the effectiveness of the runeword, you want a weapon that is as fast as possible. Although the damage on the warpike is very good, the merc will attack very slowly with it. I would hold out for a weapon with 0 base speed or faster... but if you have Um's to throw around.. knock yourself out.
yup, warpike is a spear so the crescent moon won't work in it. The only thing I could see using that pike for is "Fury" (Jah Gul Eth) Jah has gottenquite expensive while gul is easily obtained these days. there are better choices for your merc but if you have the runes to spare I think a Fury eth Warpike would be fun.If you want to make a crescent moon then look for an eth 3 sock ogre axe or great poleaxe.