Have you tested any of your prints to see if they're water tight? That's not an easy feat, but figuring it out also won't require an enclosure. I once tried printing a pool part out of PETG and it filled with water very quickly - you could see it whicking through the layer lines. Once you nail water tight printing via tuning, a TPU gasket should give you a pretty decent seal.

Are you looking to go multi-matetial? I've run quite a range of material through my stock i3 extruder and also my Rapido HF on my stealthburner. Both extruders have handled a decent range of materials without a ton of fuss.

I went for ASA over ABS because it has a reputation for being lower odor and easier to print. If you've figured out PETG, ASA won't be too hard. Natural colored ASA was super easy to print. Colored ASA needed a lower extrusion multiplier and was more prone to warping in my experience. Don't rush either (do a test print, clean and level your bed, use an enclosure) and it shouldn't be that hard. Assuming I had a clean and level bed prints were pretty uneventful. I went for 100 bed / 245 extruder. The only small gotcha was needing to PID tune at the higher temperature.