Can you please elaborate more on the problem you're facing. If I'm getting you correctly you want to have several different master pages but the same navigation on all of them. In this case, why don't you use nested master pages
and place the navigation in the parent and do the customizations in the children, or whatever logic suits your purpose. If the functionality you demand is different, please inform me, so that I can give you a better advise.
the Telerik team