How to make a "One Wet Tyre" rule enforceable.

[Adam43]

There has been talk of keeping the One wet tyre rule, but somehow forcing the teams to bring a proper wet tyre. I don't see how this can work.

It would be relatively simple to define a minum tread depth or amount of thread, but I would have thought that there is a lot of difference in the compounds of a wet and intermediate tyre too. It is the compound which governs how well it comes up to temperature in the different wet/inter conditions.

Additionally, I can't see a gentleman's agreement working. It would come down to which manufacturer pushed this to the limit the most!

IMO it would be better to go back to allowing more than one wet tyre, but if you had to have a rule that allowed only one how would you write this rule?