I use a propane burner but with a griddle I would think the heat is going to be so diffused over a wider area it may be difficult to get up to temp and pressure without using quite a bit more gas and time. And you'll have the contact surface issues too - no air circulation between the pot bottom and surface of the grill -that doesn't exists when using a burner.

Can you find a model that allows for conversion - ie: 1/2 the griddle lifts off and burner can be used directly or part of griddle can be replaced with a regular burner?

Dave