Why are you interested in the contrast extremes?
The negatives, I had, which needed contrast extremes, were not worth the printing time. Trash! (Well, that's where most of my negatives and prints are anyway.
Also, dichroic heads can easily do ISO-grades 0-5 on most papers. What they can't do is match the contrast achievable with filter numbers 0-5. The two are not the same (not even filter numbers among filter manufacturers are the same, not even close), and ISO-grades 0-5 are just fine. For the few prints that deserve the time to print at contrast extremes, keep a set of under-the-lens filters around, just in case.