Thanks all for the kind comments! Yes, I have kept busy...and these projects seem to take about twice as long as you imagine they could. I'm glad to not have to scrunch around dark corners on my back for awhile.
Marine circuit breakers (or, for those who feel really rich, aircraft ones) would be a nice upgrade. I don't know that it's in the cards for the foreseeable future. So far, at least, blowing fuses has not been a regular occurrence for me, thankfully.
A large inverter/charger and appurtenances does have its advantages, to be sure, but would also be rather intrusive to install, particularly to have a setup sufficient to microwave (which would seem to me to be the main selling point). I'd pretty much have to convert some storage space to battery space, as the battery tray only holds two batteries, and run lots of big wires to and fro underneath stuff, and so forth. The work doesn't seem worth the outcome for my uses, at least now.
I have been toying with the idea of installing some solar capacity at some point, though have no solid plans to do so. Thus far, at least, I've generally ended up either camping where there's electricity available or only staying in one place for a night or two, with decently long drives between, so battery capacity and charging hasn't been a difficulty.
Probably the next sort of large project would be upgrading the dash radio from vintage 1998 to contemporary. It would be nice to be able to play something newer than cassettes (I do have one of those cassette adapters to plug into a headphone jack), something that can display an image from a back-up camera, and maybe even something that doesn't tend to have the left front amplifier channel cut out randomly at low volume settings.