Given that Indian Wells and Miami have a joint event, they could easily hold mixed events. Cincinnati also. the doubles players are hardly overrun at the big events, so they have capacity to play. So there is potential to grow it if the demand is there. Put 7 events together and it is possible you could create some sort of circuit and effectively play into the top pairs playing off in a year end event.

The biggest issue in all that ? ATP is for men, singles and doubles. Job done, O2. WTA is for women - job done, Singapore singles and doubles. Mixed doubles has no promoter or organiser outside of the individual slams. But if someone would take it on, the events are there and the demand is probably there as I think many people enjoy mixed events. ITF cant do it, but ATP and WTA together could conjure up something and I could see a top 8 pairs event possibly working. It would need to be almost certainly be in the USA. But why not and a TV channel would almost certainly go with it. If they buy a ATP250 event, they would buy a mixed doubles top 8 event no problem.

Or perhaps I am miles off!!?

Edit - I also meant to add that with a few more events, and some sort of structure to a series of mixed events you could also have a ranking list or race style list- mixed currently has no context or structure. Like Test cricket, which has no linkage of one series to the next,  I personally think viewers and media needs context and structure around sports to make them more relevant