surely it can't be that bad to go to APSC? Seems like basically all the modern A-mount stuff is designed with APSC in mind, since as you noted Sony only ever put out like four models with full frame sensors. And APSC is about halfway to full frame, you'll only have 1.5x crop factor to deal with instead of 2.6x, as I understand it?
As an alternative, you could always go to Sony's mirrorless line, which they've obviously put a lot of love into, and pickup an A-mount to E-mount adapter for your Maxxum lenses, those seem to go for peanuts secondhand. That gives you the original a7 as a fairly reasonably priced full frame option, at least by comparison. It seems like some features were dropped in the A-mount to E-mount transition, but if you're coming from a film camera, that might pre-date those features? Of course, mirrorless means you're going to have a digital viewfinder instead of optical, if that bothers you.
Please take anything I say in this comment with about 60% confidence lol, my credentials are simply being a general-purpose nerd, so I'm just vaguely familiar with the models at a distance, I've never used an interchangeable lens camera, I was just fascinated with my dad's as a kid and never grew entirely out of it.
edit: okay, I caught up: looks like the features lost from moving from A-mount to E-mount mostly impact lenses for film cameras. you'd need a much more complex adapter than I was looking at to continue to use the autofocus on A-mount lenses, and if you use the Sony adapter you're looking at not only $250 for that, as well as having to use a higher end and more recent model from the mirrorless line like the a7R IV or a6600. :/ so perhaps sticking with A-mount is the move if you want to keep using your Maxxum lenses.
