Hi,
I think I kind of get what you're looking to do, but I'm not sure that you'd want to tackle this account of coding in an iRule. You could definitely build an iRule that displays a webpage with a form, and have that form post the info on whether a virtual server is in Normal or Maintenance mode, but there will still need to be a receiving application that takes that data and then makes the change on the F5. Plus you'd need a way to query the virtual server(s) and get the status back.
It seems like it would be simpler to have a one-page website that communicates with the F5 via iControlREST and gets and sets the status of the various virtual servers. If you want, you can have the page make a REST call that adds or removes an iRule on a specified virtual server.
-Joel