In answer to your general question...
TALK TO YOUR PRIMARY.
Seriously-the only way to find the answer to whether YOUR V can become a Triad is to ask.
There is no "rule" that says ALL poly relationships must be type N or N+1 or N+2 etc.
You make the rules. But that means you have to be open, honest and caring with YOURSELF and with each other(s) so you can FIGURE OUT what the rules are.
I spent all weekend working on "rules" with Maca (another poster, also my husband).
Currently we have a V. We are married and I have a BF. Both my BF and my husband are straight, so no triad coming from that.
Maca has been entertaining thoughts and building a relationship with a woman who is married. She's bi-curious, her husband is bi (yes they are all well aware and it's on the up and up).
But it's a new dynamic for us-so we had to discuss what was ok and what was not ok.