The problem with explicit wording is that some player/lawyer will look at the list of forbidden things and come up with something you didn't think of. It's impossible to guess how inventive players will get. One word: Deuel....
This is an area I think the BCAPL rules are significantly more explicit and make it clear what is and is not allowed. Usually in scenarios like this I highly respect whatever Bob Jewett has to say on the matter. It’s always wise and logical. It’s just a bummer WPA rules don’t have explicit wording to reinforce that perspective.