Well... hmm... This is quite complicated indeed.

What I see as the most reasonable option:
Ask his (then her/her significant other) permission to have one kiss/what you wanted to try that would be permitted.

My reason is mainly that it will likely bug you and distract you always wanting to know what it would be like.

Now, you said he may be worried/insecure, so I think talking to him for quite a while about this would be the best thing. What I've learned with my wife is that honesty is the best policy. Hey, you might even learn something about each other by talking about it.

Also, another option... would be asking a "hypothetical question because you're curious", about what he'd think about it before talking about it.

o.o Just my opinion though, but if my wife had something like that on her mind I'd rather her talk about it.