Because I know you’re all dying from suspense, I’ll let you know that the pesto risotto turned out really well.
What I ended up doing was leaving the onions out of the risotto and using a couple of extra cloves of minced garlic instead. With the pesto, I cut way back on the oil, just adding enough to make it a thick paste rather than a sauce. Then, when I added the last of the chicken stock to the rice, I added the pesto paste as well so it would break down in the stock as it was all getting incorporated.
I probably should have stopped the cooking a little earlier so the risotto was a little soupier, but it tasted really good. We had it with grilled chicken.