Had spacesuits been used in TAS, fishbowl helmets and color variations by division should have been more than enough to make the characters recognizable and distinguishable. The point that the diving suits in Sealab 2020
worked well enough is all the proof needed to show that spacesuits could have worked adequately
Regardless of the advantages in production to using the life support belts, and it's been clearly established that there were definite advantages in both character recognition and animation cost, it's worth emphasizing again that the concept of the belts was one originally conceived of for TOS, in order to demonstrate that it's unfair to assert that Filmation, say, "watered down" TOS tech to adapt it to animation. Additionally, the point that continuity issues with later shows exist only because the later shows failed to use something similar to the belts
is a good one, I think.