Would it be worth retagging questions which are making synonym requests as synonym-request. From what I see here, it sounds like the mods could perform this sort of soft-tagging without bumping everything -- sorry didn't realize that this would bump questions and stopped when I noticed after the fourth question.
We don't need a separate tag for synonym requests. The proper tag is retag-request.
If we do a bulk retag job, the implication is that the tags are identical in meaning - they should be made synonyms after 90% of these jobs. The exceptions are disambiguations and the like.
The importance of making a synonym request is not as much the creation of the synonym, but the changing of all of the existing instances of a tag. And that's really just a retag-request. You can simply just slap a "Please do/do not make this a synonym" in the question body, if it must explicitly be said.
If we created the synonym-request to categorise those requests so yes it is interesting to retag question for synonym request if they are still live: i.e. not competed or denied.
We do not need to "necromance" all synonym requests by retagging.
On another hand, I do not thing that the synonym-request is useful by itself since we have tag-synonyms and feature-request. Both of these are equivalent to synonym-request. Or feature-request is mandatory, so synonym-request is just too much.