just to clarify a few things here amongst all this generally good advice. both analog and digital goggles can have receiver bays and hdmi in, but not all of them do. it doesnt have anything to do with whether the built in transmission system is analog or digital. the video output of an analog goggle just might be composite.
walksnail released the avatar gt2 in April, so they are still actively releasing things for that system, but it probably wont be in production that much longer. none of their goggles have a great reputation though and many people dislike them for how long they have left issues with the goggles x unfixed, despite it just needing a firmware update.
you can get good image quality with analog, its not like its always fuzzed out or anything, in fact, there are many situations where I prefer the analog break up over the digital, which can just suddenly cut out instead of gradually warning you. An 800 tvl camera is not going to be the same as a 1500 tvl camera. Thats another bonus on analog, you have dozens of different camera options from nano race cams to full on thermal.
hdzero goggles are technically the most versatile out of all the options and no ones mentioned them yet. They have built in analog and digital, as well as hdmi in/out, and additional receiver bays. as well as design files available so you can model your own accessories for them. they even have a vtx that has hdmi in so you could use a GoPro/cinema camera for your fpv feed.
with whoops, bnf availability doesnt really matter, to build your own with an aio youre generally just talking about 4 motor plugs, some screws, and a camera connector.