What I would be looking for is a higher, more vertical, seating design that SUVs have. Also more cargo space behind the second row of seats; 25 Cu Ft would be a starting point. A hatchback for better cargo handling. True fold down rear seats, not the small hole of the Clarity. Beyond that I won't buy another PHEV without at least 50 miles of EV range. Acceleration isn't that big a deal for me evidenced by the fact that we had two Prius cars before the Clarity, and we drive in Econ/EV mode all the time. Won't be a problem fitting in the garage; our 4Runner fits. I doubt if it would have compromised rollover safety because the battery weight lowers the center of gravity.
I would be thrilled to move up from the Clarity sedan to a small SUV PHEV under those conditions.