To keep it short, I love what you have in mind for Will and I think Duncan would be in FAVOR of Will's right to autonomy and side with him, so he would reach out to help him find closure and put the bastard in jail. He isn't in favor of abuse, but he knows there is a fine line between control/power and abuse. Too often people cross that line.
I'd LOVE to plot something with Brandon, he sounds just like someone Duncan would get involved with for better or for worse. I think he could be a lot of fun and great and sex? yas queen also I think Mateo would be fun but lets stick with Will and Brandon for now? Mateo he might know and have relationship [friendly] with simply cuz it looks like he is going to be besties with Lucia if things go well.