LTM User Role: Apply iRule to VS

I'm relatively certain that there's no user level that will allow just adding/removing a rule.

However, there are other options that can accomplish what you're looking for, like iControlRest (https://devcentral.f5.com/wiki/iControlREST.HomePage.ashx). You could create a hosted app (including the required security) that in turn can affect changes to the VS.

Another option would be to use a sideband connection to check a specific flag somewhere in your environment, like the absence or existence of a file, content of a file, database record, etc.