I like to search by tags. Sometimes I feel that a well-written question would benefit from an additional tag, however, I can't add a tag without editing six characters in the body of the question. What's the reason for this rule?
This rule is in place so that newer users who don't have much rep (who usually don't know the site well) can't just edit all they want. You get full editing privileges at 1,000 reputation, so only users with 1,000 or higher can edit without having to suggest and get approved.
The limit on how little you can change a post before you get the editing privilege (you have to make a somewhat substantial edit) is there so that new users don't go around spamming, rep-farming, or even just bumping up dozens of old posts just to fix small errors.
In your case, I think you're trustworthy enough that if everyone was like you, we wouldn't need these rules, but we don't have the ability to make exceptions, so you will have to keep going until you've gained the editing privilege.
Now I find that when I want to retag something on a site where I don't have full editing privs, I can also try to find some way to improve the site while I'm at it. Even rephrasing a hard to read section is usually substantial enough that I can submit the edit.
I'm glad you want to help make this site better, I encourage retagging, glad you are ... yeah, just said that... Even cool users like you have to play by the sometimes seemingly unnecessary network rules. But there is a way to get the privileges, and you already know what that is.