One potential problem with this idea is that if the triad or vee breaks up, the child could well end up estranged from one parent. This can happen when couples split up, of course, but, at least anecdotally, it seem like poly configured relationships are harder to keep stable in the long-term versus the traditional mono pairing. So it would seem like the chance for the child to lose a relationship with a parent could be higher.
Then again, this would potentially be an argument against poly co-parenting too, and I'm certainly in favor of that in the right situations. But is it more damaging for a child to be estranged from a biological parent versus an adoptive parent?
Of course, this is wildly speculative... still, I find it interesting to think about.
I suppose some MFM triads or vees might already do a similar thing... they could just have each of the males have unprotected sex with the woman on a regular basis, then not test for paternity...
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.