Personally I've been in favor of Gonzaga but the fact that the Big 12 didn't add them after a year of rumors (plus being much more geographically aligned) tells me there are massive roadblocks. I get the sense it may not work financially for one/all parties, and I don't want the Big East making a western division to accommodate them. The other western basketball options just aren't very good.
I'm not against ESPN, ideally I'd like them to get some content, but Fox has been a very good partner and may have more influence than ESPN in regards to conference realignment. I'd be fine with either/both but am against making Amazon, Apple, or NBC our primary partner. This interview indicates we'll stick with a company like Fox, fortunately.
As for the ACC there's a new rumor every week that Clemson, FSU or UNC are on the verge of leaving. By the time we'd start a challenge half the teams would be SMU, Cal, Stanford, and likely teams like USF and Tulane. I think Big Ten is the best partner in the country, which we'd only get through Fox. SEC would be second or maybe third after the Big 12. ACC dead last now that the Pac is gone. The merging scenario you mentioned is a possibility but I don't think likely.