The synonym system needs an overhaul. Right now, there's a synonym request tag, just because of how useless the site's synonym system is, where on some SEs at least it is encouraged not to use it, as you can accidentally screw up the tags and it's hard to fix. It's also hard to find and use, requiring several levels of menu navigation.
I figure a lot of changes are needed, but the foremost would should be to require moderator approval for a new synonym, since they can cause unforeseen problems.
Tags could still require four votes to be accepted as synonyms, that way, and moderators would get a list of 4+ vote synonyms they can approve.
You could then lower the privilege of suggesting synonyms, with the hopes more people will vote on them and moderators can peruse the most popular suggestions, as right now everyone just uses metas (there's a tag specifically for it, ironically) and the whole system has gone to waste.