Coral blocks should have blockstates or should be preserved like copper

If coral blocks were a block state as opposed to what they are now, perhaps similar to how Redstone lamps work, that means that with commands, or a debug stick, coral can toggled to always remain alive and would not automatically update with randomtickspeed 0. 

Alternatively, there should be a way to preserve coral similar to how copper is preserved, although probably not through waxing as it wouldn't make sense. Maybe you could "hydrate" it with water bottles or something, or maybe there needs to be a new gameplay mechanic for it since coral dyes really quickly

if you want to keep the current survival method of keeping coral alive, then I would recommend going the block state route, but it might be a good idea to try and be able to find a way to them alive out of the water in a way that makes sense, especially with whatever message you are trying to send about the coral reefs. Either way, there should be a way in creative to be able to keep the coral block's color alive permanently.