Of the current accessory range - I would definitely keep the Magic Balls for decanter cleaning - something I use quite regularly - and the Drop Stops.
Other things I would consider:
My Screwpull corkscrew is still going well after ~20 years of regular service. Probably something similar warrants a place on the list.
A friend gave us a couple of Vino Chapeau, which do actually work for concentrating wine aromas and making tasting notes easier to write.
If you don’t want to run to an eto for keeping wine, I have found 200ml glass bottles that take a Vinolok glass stopper work well for keeping wine (sometimes for weeks at a time if well filled). Being able to buy such bottles and some Vinolok stoppers might be useful e.g. if practicing tasting for something like WSET exams it allows a few tastings out of a bottle.
Wine glasses often attract strong opinions, but personally I would put the Zalto Universal glass on the list. Dishwasher safe, it’s a really light delicate glass, that provided you don’t try and wash up by hand has good longevity too. We use them as our everyday wine glass and put them through the dishwasher every time.