> Am I correct that there is no way to either change the approval or improve the edit (until it's approved, at least)?

Yes, the only thing you can do is **wait until the edit is accepted/rejected and then improve it**. It will be boring, so I suggest that you copy the content somewhere and do the improvements and then just apply them to the post.

[.][trick]

 [trick]: http://meta.stackoverflow.com/questions/270537/trick-the-suggested-edit-queue-to-force-reject-items#comment89363_270540 "there's a trick to just try to edit the post using url/posts/id/edit, but it will reject automatically the suggested edit since you are overriding, through this will change in the posterity"