My husband and I try very hard not to have rules based on limiting our other relationships' ability to grow however they might. Our one rule, other than safer sex, is that we both make sure we spend time and energy nurturing our marriage so that it remains strong. Making a rule that said we couldn't kiss any one but each other just seems so incredibly limiting, which is not what our poly is about.
Really, what you're describing sounds more like an open relationship or swinging to me than poly. Poly, although it includes having sex with others, is more about the relationships than just about the sex. While having an open relationship or swinging tends to focus more on the sex.