I brought up playing my Greenskinz as Bonesplitterz a while back and some people thought it was bad form to use one model as another just because it had better rules. We're in a weird spot right now as Greenskinz still have points and warscrolls. Maybe when the book comes out they'll move them to Legends? It seems like that would do away with the objections some people had, and in some ways would be more merciful then having the Greenskinz continue to limp on with no support, but I also understand why it would make some Greenkinz players sad that their army no longer exists in the rules.
Some people thought that it wasn't good to run Greenskinz as Bonesplitterz because they looked too heavily armored, which I understand. Some of those same people thought they were better suited to be run as Ironjawz, which I thought was weird because to me they look too small and under-armored. They're kind of in a weird place in the middle, but it wouldn't bother me to see people running them either way.
I think it's interesting how people have differing opinions on what it appropriate. I'm guessing most people will be cool with whatever as long as it looks good.