Thanks for the chapter!
Mystic set probably only looking at Changkong based on his martial spirit rank, whether they're stupid enough to sign him up despite his hubris and arrogance is another story. On the other hand seems the usual template are all the strong fighters proving that power corrupts and absolute power corrupts absolutely and therefore act like bullies who can treat everyone like ants based on their high rank, clan, and/or sect with ones who are humble and responsible like MC's father being the extremely rare exceptions. Hence they might think to sign him up while considering his arrogant personality to be par for the course as long as he doesn't cause too much trouble. In any case, Changkong is probably going to have an aneurysm after MC not only outclasses him, but gets the offer instead. Also, just what kind of family values are they teaching where family and clan members want to kill or ruin other family or clan members out of arrogance and/or imagined affronts due to not getting their way like a spoiled brat.