In my opinion, that's the best place to start. IF the OW is gone, and he is willing to do that, no questions asked - then, and only then, in my opinion, can there even be a TALK of reconciliation.
If you require that of him, I would also be honest with him about your feelings. Let him know that if he completely pushes her away, it still may not result in reconciliation, but it is a requirement to even CONSIDER it.
If he doesn't respect that, then he's an idiot, and truly hasn't seen himself in the light he needs to.
I would say him "going out physically" obviously didn't do a whole lot for him - so what would it do for you? Wouldn't you just sort of feel soiled?
Quite honestly, if W came back to me, I wouldn't even want to know if there was a physical relationship - I don't know at this point. If I did know, I would require a full-scale STD test. Not very romantic, but oh well. If the test came back clean, I wouldn't ever mention the relationship again, keeping in mind my rule about zero contact for the rest of her life. I mean if she walked by him in the grocery store, she better leave her cart with the groceries still in it, and walk out - just in case he might try to say hi.
But that's me.
The feelings are a tough one. I love my W dearly, but I'm not sure if it's worth taking a chance on getting hurt again, just as I'm getting over it.
Honestly, thinking about going through the pain again makes my stomach hurt.