I suppose anything is possible... but why an oil burner?
OK... let's go with your assumption. I'd say that you'd have to figure-out how to have the engines run at the same speed at the same time. The output (crankshaft) would have to mate to a common gear to apply power through a transmission. That is, of course, unless you want two transmissions also. If you went with two automatic transmissions (with two torque converters) this would help compensate for the varying RPMs of both motors trying to run at the same time. (Two motors will unlikely turn the very same RPM at the same time.) But by the time you've mounted two 2-stroke motors, 2 transmissions and the reinforcement required to hold them motors in the rear, I'd say the Elise's front tires will be a solid 4 - 6 inches off the pavement!