If you believe I will ever have any interest in building a community on Stack Overflow for this niche, you're wrong.
It's your way or the highway? If you don't get a dedicated site for Appcelerator, then you're not going to even try to build a community for it on SO? That's sad and unfortunate.
The solution to Stack Overflow not having drawn enough of a community around a certain API is not to create an alternative site. The solution is to work to build that community yourself. The solution is to get Appcelerator developers to ask and answer questions on Stack Overflow.
If you do not like that solution, then it is unfortunate. But that's the solution we offer. We have one site for answering programming questions; it's called Stack Overflow. We don't segregate people off into their own little APIs/Languages/etc; that's what tags are for. If you feel that you need that segregation, that again is unfortunate. And if Appcelerator developers truly believe that Stack Overflow cannot work for them (not simply "doesn't yet work", which is where things are now, but can never work), then again, that is unfortunate.
The evidence shows that SO can serve large and small concerns alike. That's how SO was built. That's how SO grew. We serve many smaller communities, from languages like Lua and Go to communities built around single APIs or technologies like Boost and OpenGL.
We welcome your participation on Stack Overflow with open arms. But we are not going to change how we do things to satisfy your sensibilities or your beliefs in what your community needs. Appcelerator is not special; it can flourish just fine on SO if you try and encourage others to do so.