If People would like Vectric to look at adding centre line tracing as an option in the trace bitmap module then the best thing to do is send a feature request to support. If eonough people request a feature or change then they will look at how it can be done.
It's not something that gets mentioned very often on the forum so there may only be a small number of users who would use it.
Your original post said you had tried other trace programs as well as the one built into Aspire & none of them worked properly, the reason for that is the poor quality of the artwork you are trying to trace, a centre line trace wouldn't give you any better results, in fact they might be far worse
As Adrian & LGM have said manually tracing is the best option with poor quality artwork & Aspire has all the tools you need to be able to do that. Unfortunately it is something that takes time to learn how to do well but once mastered you can reproduce just about any image regardless of how bad the quality is