This is a fine thought.

My own reaction is that there would be a lot to be gained by using pods that are mostly on the bottom of the wing with pusher motors. The big advantage is that it would leave the more critical leading edge region and upper surface clear of stuff that could introduce drag and turbulence to disturb the wing and act like permanent spoilers. Also the pods could be short and the props would fold into the slip stream behind the wing and without worrying about fouling anything.

The pods would be shaped and sit much like the outboard flap linkage fairing to the right of the outboard engine nacelle in this picture.



But you know the best and easiest way is still the nose mounted motor. But done right and with internal wiring wing mounted pods like this could be made removable and you still have a pure glider..... Hmmmm...... You may be onto something here.

I see a Bird of Time with two Speed 400 or 480 motor pods on the wing and a belly mounted blended fairing that houses the motor batteries. Less than five minutes to remove some nylon screws and put a couple of small wire access covers back into place and you have a pure glider once again.