Well thinking about it (and if this is already doable I apologize for not finding the info) and this being a theoretical wishlist... and not sure if it's open solo specific... but...
1: I know you can adjust the circumference of an orbit shot on the fly, but how about a spiral smart shot? You set point A to start at a certain height, point B finishes at a certain height (hopefully not slicing your face off...), fixed or adjustable number of circumferences around the subject matter and just use a pinch movement to expand or contract the distance between each lap. Thinking it might be a good way to get a cinematic type shot withing having a person face down in a controller constantly adjusting the orbit shot or having to use mission planner software.
2: Parked video. Solo battery actually lasts quite a while when it's not flying (duh!). Possible option of flying solo to a location, landing, video keeps recording, than after a set amount of time it takes off and flies back to preset location. This might be good if you want to timelapse yourself or video yourself doing something from a different location, but taking more time than the flight battery allows in the air. Hmm maybe it should be called "Sitting" mode. Only problem I can see is if you land and there's poor GPS signal, you'll need to be in manual flight range to get bird back.
3: I know Hackster has a project for a precision landing system using an IR lock, however that requires additional equipment and modification of the solo. Any way to use the gopro (pointed straight down) at a landing pad and optical recognition to do a non GPS assisted landing (print our a large pattern to put on a landing pad etc). This is more of a software thing sure, but might be handy for people who lose GPS lock when landing in a poor signal area and aren't comfy using manual mode (gusting ground winds), or just another really cool feature to show off.
4: Better Hat, T-shirts, stickers and coffee mugs.... come on folks, 3DR solo has had it's moment to shine brightly, but now it's time to start proudly declaring our support for "Open Solo"....
5: I still like the "Beer" suggestion by the way...