Sounds like a fun, and insanely expensive project
I have the same problem as you - I am constantly changing my collection focus, buying, selling, and repeat. Flip flopping from vintage, to prospects, to stars/HOF autos, 90's inserts, and back again.
Over the past few months I have seriously considered just not collecting anything, because I can never decide.
Just recently I decided to embark on a larger project - basically a who's who of every MLB team - collecting all on card autos of the HOF players, as well as stars/iconic players or from each team. We shall see how long this keeps my interest
I would say with respect to your post, there are cards that are not necessarily rookie cards that are sometimes just as iconic, or at least just as nice for a much lesser cost.