It's hard enough now to get Senate confirmation of Federal judicial appointments, including those of Supreme Court nominees. The prospect of multiplying 9 appointments by a factor of X, presumably in one fell swoop, is, um... not pretty.
And, in any case, I don't think that having more than one group of judges as the final arbiters of Constitutional law would work out too well -- there would inevitably be conflicts, and what then?
"Once the writer in every individual comes to life (and that time is not far off), we are in for an age of universal deafness and lack of understanding."
(Milan Kundera, Book of Laughter and Forgetting, 1980)