Yes, thanks for making this topic, Aldaron.
I, as well as many others on the site, I'm sure, am interested in figuring out why certainly un-breedable Pokemon have only certain usable IVs and natures. However, this will be no easy task at all. If you'd like to help, it'd be appreciated if you have at least SOME knowledge of:
1) PIDs or PVs (a descriptions can be found at
Bulbapedia)
2) The binary and hexadecimal number systems (these can be found on Wikipedia)
3) Pseudo-random number generators (also Wikipedia)
If you'd like to help, I'd greatly appreciate it, but if not, I can understand, because something like this certainly won't be simple.