As the chemistry is fairly expensive (far more so than the cheap RA4) it might make sense to use new paper and new chemicals. At least your results would be repeatable doing that. There is/were a couple (maybe only one, but I can't remember the name) of labs in Oz still producing Ilfochrome - maybe you could approach someone there to make a few prints for you ?
A couple of decades ago I used to work in a lab including producing internegs for positive-to-RA4, projection printing with 5x4 darkslides to hold the interneg C41 film. We never did any Cibachrome/Ilfochrome so that was our route to prints from transparencies. I doubt the copy-film is still made these days
If you go with C41 film after all, then have a look at Ektar.
I got a box of almost full 100 sheets 8x10 Ektachome Radiance gifted to me a few months after I had fought to experiment with reversal processing RA-4.
I could find no reference to it anywhere in my old photo documentation from the late 80's and early 90's.
Kodak had a deleted product sheet for a clear on actetate version on the web that I used as an exposure and filitration guide, and it was almost spot on first time.
I mixed the first developer from my ra-4 tests, gave the best exposure guess, developed fd in a tray, stop bathed, then optically re-exposed the usual low contrast b&w print aI have learned to expect for a good reversal colur print, rinsed, fed it into the roller processor for normal RA-4 processing, and got a great print on the first exposure.
No cyan shadows and pink skys like the best of my ra -4 efforts, after 15 prints.
I have not had the time to get back to it yet, but am not going to part with it. It is living in the paper freezer with the rest of my stash.
I have too many great old Kodakchome images from my departed dad and grandfather that I some day will find the time to print with this stuff and hang on the walls
Any reason for excluding Ilfochrome other than cost?
That's reason enough. I'd happily jump back into Ilfochrome printing if it were half the current price. I'd also prefer it being readily available instead of special order but apparently that doesn't take too long.
And if that sounds like a silly wish, the current prices I see for paper+chemistry total about $5 per 8x10 sheet. RA4 is a buck or less depending on how and where you source it. So I was going to jump back into RA4 instead...except that, apparently, the Fuji Type II paper is all you can now get in sheets other than left overs, and most people report bad results with it optically.