I don't know if I am an expert, but I have done a lot of creature modifying, so I am pretty solid.
Most of this is really OOD, and so it isn't exactly relevant. I mostly did stuff back in v28. I built a gnat that could kill a giant (NO_BREATH was an annoying necessity, as the d@m giant kept suffocating it before it tore him apart). I built wolverine, and I built a pretty solid xenomorph. (I gave up trying to get the chest burster working without dfhack) I love modding the genetic code of DF creatures.
I also am avoiding it as much as possible until TOADY finishes....If that's in my life...
Note that I modded everything down to the smallest detail I could find. My creatures were as close to 'genetically' pure as I could make them. It was also an almost complete waste of time.
Toady added the ATTR and that is definitely the easiest place to start. Those values are honestly SUPERIOR in priority to any of the others. I haven't tested it too see if/how it has been balanced, but a character with STR:5000, TOUGH:5000, and END:5000 was/is tougher than steel. I would be surprised if those values are now inferior in priority, as that would have involved a major code rewrite. I would also be surprised if they were still tougher than steel. Toady has surely balanced them in the background.
What do I mean?
STR * (Whatever bone changes you make to the bone and muscles of the creature) is how it appeared to be built. Not:
Bone material values * (Str + End + Tough)
The reason is that the 'strength' of an individual isn't limited to the properties of the materials in themselves, but also to the scale, size, and dimension of the interlocking parts. This is a mechanical engineering problem, and I am ABSOLUTELY certain that Toady hasn't figured out how to model leverage (Otherwise a castle couldn't stand on one support). The game runs on individual cells and cell structures. If you change the materials of the Femur Bone alone, it does not provide any meaningful change to the creature as a whole. Just a cosmetic one.
My guess is Toady is trying to figure out how to model the real deal, but he is barking up the wrong tree. That's why he added STR, END, TOUGH tokens to allow the game to model variations in the physical prowess of the characters, and why I mean they are superior. He probably needs to completely rebuild the code to get it away from its current design. Anyway, I love talking creatures, so you are in luck there.
If you need cash/work, I would also being willing to help, but I would want credit and a thank you [LGL DISCLAMIER - OK, technically if I help you get a point where you personally get reliable revenue for my services rendered (IE a patent) I would expect 5% royalties, but you are just looking for work so it isn't that relevant]. Also you would need to answer a lot of questions. I love design work, digital creatures or living ones, makes no difference to me. I love to play Igor.
*Laughs Maniacally*