Well, four refinery hubs and some luck with a planetary port seems to be good enough to retain a majority of its refinery exports despite the volcanism applying industrial to it. Only things it's missing are ceramic composites, copper and semiconductors, but instead it gained liquid oxygen, aluminium and polymers. Coriolis in orbit still has more or less the same supply offers (semi(superconductors, steel, titanium among important ones), despite increased industrial presence from the planetary port... which surprised me. Both seem to have 4.8 refinery proportion according to the journal.
(So in effect I have most bases covered now except the ceramics, which I already have plans to build a port and refinery hub where I know I'd get them issue-free... because the planets there don't have volcanism)
... think I will leave this refinery to be as it is now to avoid losing any of those exports. It's "good enough" as its interim state.