Hi jc,
I believe that you are right, first be careful with thermal disipation, with proper heatsinking at output transistors.
With lateral mosfets there is positive thermal coeficient, but vertical mosfet have negative thermal coeficient and must be cotrol temperature, generaly by putting a transistor in thermal contact in heatsink. With lateral mosfets is more easy to implement.
Another problem is the power supply. In simple power supplies (unregulated) is easy to raise quiescent current, but active or regulated PSUs is some difficult and heatsinking and/or unwanted voltage drops can occur.
Regards,
Luis.