IF you discard the BGS, what do you have? A game running in a frozen Galaxy where nothing ever happens.
An offline version could have a MUCH smaller bubble. X4 [spits on ground like Corner Gas crew] has a much more detailed "BGS" that works perfectly well offline, but it also has a much smaller set of systems to update. Not sure how this would be handled lore-wise. Perhaps the offline version could be "Elite Dangerous - Post Apocalypse" where all but some of the core systems have been invaded and wiped out by Thargoids.
Now whether Frontier would want to invest the work to make such a game is a totally different question. I suspect the answer is a very loud "NO!" considering the history of the originally planned offline mode. My personal dream would be an open-source version of Horizons, then we the people could make an offline mode, but I know that'll
never happen, regardless what Braben might have once said.
BTW, No Man's Sky (a game with an offline mode) has no BGS that I'm aware of, and people still find enjoyment playing it, so I'm not sure a BGS is a mandatory requirement for everyone. I don't know how NMS does markets - I'm guessing it's just a locked proc-gen price for goods that never changes over time, but I'm very open to correction.