I don't know if somebody has already mentioned it (if so, then forget about me), but I think it could be interesting to get the cum layer 'thicker'.
Like, once an oral adds a layer around the mouth, then another oral adds another layer to cover the lower face and +1 facial thickness level, then another and another... 'till cover up the whole face. Viginal and anal sex likewise, covering up the body, sticking in between the legs or sth when reaching the max thickness.