Sure, no doubt more people can be a good thing. I've talked about it with children of polyamorous parents, and my impression is that parents having multiple partners isn't a problem as long as it's all in the open, and the core mother/father pair remains intact. I think the research backs this up too (at least, that a core mother/father pair is ideal), as does common sense if one considers it in comparison with possible alternatives.

Indeed, the bible doesn't condemn polygamy (which is not the same as polyamory, I note), but it also seems to indicate that it's not the optimal state of affairs. I think the bible treats polygamy as an acceptable solution to a bad situation; not a scenario to be sought out.