I think thri-kreen was already done wasn't it? Project Q I think and/or CODI. Converting it to playable humanoid might be as easy as converting it into a "skin" you can wear in the "robe" slot. Then all you need to do is make a few custom overlay parts for the chest and what not. It wouldn't be too difficult to actually make the character. Making it customizable in the same way human and elf are with the gear is what keeps people from bothering with such things. The problem in doing that is that you have to make parts for the new race which line up with the OC races. But not only the OC parts. You also have to make parts for all the custom OC race parts that you have.
The alternative, and I've used this before, especially with skinned PC's, is to make race specific armor parts. This lets you completely change the order of the armor parts built in fitting system. You can then bypass any appearances you don't want to duplicate from OC races, and just work immediately forward.
I did similar with my skinned characters, because I gave each skinned character a different physique. Belril was always in a robe, so I affixed it to his character as a skin option, and then made only the parts I needed that would poke out from under ALL robes, just in case he switched on me. For Nania and her twin Nacia, they had smaller teen female physiques, so they could wear parts on their chest that the larger women could not. Since one was a rogue, and one was a sorceress, they had a lot of form-fitting gear that could not be worn by the warrior women of different shapes. Ernin was not exactly large, so the normal human female shapes could fit her body. On the other hand, literally, Jennica was missing an arm, and had interchangeable parts for the limb, which needed special treatment when considering weapons. Most of the elves were able to use super basic models, but two of the drow had to be custom. First there was the drider Raist, which I designed as simply as possible, because nobody wants to make that much gear for such a creature unless you are going to use it A LOT. He's a very specific priest, so I didn't see a lot of point to going into depth with all the possible combinations, since for the purposes of my modules, you would never be able to play a non Raist drider. On the other hand, there was a need for multiple larger male drow that the base elf model could not accommodate, so I further fleshed that out by working more with the OC human model.
Perhaps what you should ask your friend is this: What is he going to do with it, and what future use will he need from it. I'm all for the lazy method of doing the least for the most. So if he has a specific need, or a few specific needs, maybe making those specific needs would be more realistic. Otherwise you are talking days of work for a single character type. And that work is specifically tedious and repetitive.
Something like a Mul is less so, because it is basically a larger human looking dwarf. You could technically get away with a few new heads, maybe some new scarred arms and legs models, and then make anybody who comes in as human subtype Mul automatically scale down using a scaling invisible dummy. That would work, but only assuming you don't have mounts. I did similar when I was working with Duergar mods. The same could be done ( I mean exactly the same) for the half-giant, unless you wanted a hunched appearance.
Alternately, such an easy humanoid clone could be made programmatically, as long as somebody already had all the model parts out and ready. I know a few on here that could do the Mul really quickly for you (not me).
