I don't do anything like enough processing to justify replenishing, and have been rotary processing of 4 x 5 in a Jobo tank, but am about to do some 5 x 7.
I'd forgotten I had a Paterson Orbital, which was designed for processing a single sheet of 8 x 10 color paper, and will do two sheets of 5 x 7 film in the way I was envisaging. I’d tried it before for 4 x 5 and not been very impressed, but from information now more easily available online, it needs some modification to prevent the bottom of the film sticking to the bottom of the tray and not clearing, the separation pegs need extending to keep the film in place, and the fins on the top may need to come off for more even agitation.
There seem to a few people still using Paterson Orbital processors. Values on Ebay vary. An updated and improved version of a similar light tight tray tank might be a possibly simpler and useful alternative product to the SP457, especially if the manufacturer is considering moving up to 8 x 10 next. In revising the Orbital design, the bottom needs to be slightly textured, and perhaps not necessarily curved, and slightly higher sides might be a good idea. Getting tray agitation even and uniform may however still prove difficult. There seem to be mixed reports about the usefulness of the Paterson Orbital’s motor base (I don't have one), especially for larger sizes.