How (un)ethical, even with an editor's permission, is it to reach out for collaboration with reviewers after the review of one’s manuscript has been completed?

Here's some background on this question. In the peer reviews of my work, I've collaborated with (mostly anonymous) peer reviewers who not only share similar perspectives but also serve as excellent examples of collaborations that could make significant contributions to my fields of study. I'm faced with a challenge-the rules of anonymity and a solution, the call for OPEN RESEARCH. How do I navigate this?