I wish I didn't have to have 5 points in a tag to be able to suggest a tag synonym. E.g. for the tag "health" I wanted to suggest a synonym "fitness" but I couldn't since I don't have 5 points in the tag "health". This happened a couple of time to me. Is there any way to relax the rules for a specific SE? That to would be useful in beta.
Community votes for tag synonyms don't even really work on Stack Overflow, so this issue isn't specific to beta sites. I'd be all for a better system to coordinate tag synonyms among experts, but that system wouldn't be specific to smaller sites, it should be used for all the sites up to SO.
If you think your synonym suggestion is a no-brainer, ask one of the moderators in chat. If you aren't absolutely sure, raise it on meta. If the discussion settles in favor, a moderator will create the synonym (if you think there's a consensus to create a synonym but moderators haven't acted on it, again, ping us in chat).
Regarding health and fitness, I don't think they should be synonyms: I associate health with, well, health issues, such as monitoring a heart condition or keeping track of your diet; while fitness puts me in mind of sport activities. There might be some small overlap but they're overall pretty different things.