How much do you care for your boyfriend? Would you be upset if you lost him, or would it be a mere nuisance? The answer to that question dictates what you should do wrt 'extreme things'.
a) If the answer is that you don't care all that much, then do whatever you feel like. Either he can handle it, allowing you everything you want...or he can't, and the break-up is small loss to you.
b) If you do care about your boyfriend, I would advise caution.
Appreciate what you've got. If he wants a creampie, there's nothing stopping him from requesting one, is there? All guys are pigs, after all - if he wants it, he'll drop subtle suggestions/ask outright, depending on the openness between you...which sounds rather great, on the face of it.
But if the open relationship thing was his suggestion, and you went along with it...well, unfortunately it does not necessarily follow that he would appreciate an equally risque suggestion from you. He may feel that he's got the control over the situation by suggesting stuff like this and being able to define what goes and what doesn't, and feel that he loses control if you forward a suggestion. An alternative can be that you drop subtle hints, allowing him to 'come up with the idea' himself.
Basically, I don't really know your situation, and neither do the cucks around here. Only you know your situation. 95% of the cucks here will respond from what their own fantasy world dictates, which may not even have the faintest connection to your reality. It sounds like you've got a good thing going, and I'd hate to see it ruined because someone had a 'great idea'.