You could also base the scaling on Psionic Body, like I did: each feat is of specified type(s), and supports other feats of related type(s) by giving them both bigger numbers and new functions.
Tying the progression to number and type of feats also has the side-effect of making the scaling more useful to the Fighter as written. It also creates an easier-to-understand optimization framework. Having a hard time choosing what feat to pick for this level? Worry not, just pick a feat of type that is shared by most of your previous feats, that way all of them become more powerful.