You can always let them know you have someone on the back burner to get them in to sign in a day or two. 

When they left they turned on all the lights, raised all the blinds, turned on all the burners on the stove and turned on the over, stuff the vents with trash, locked the doors leaving the keys inside so we had to break in. 

That being said nat gas can be much more efficient than oil burners.

It already has a new gas burner, but the steam boiler itself is old.

I'd consider simply changing over the burner on the exiting system to gas and not trying to split the heat.

Resistance burner ovens have an extremely long life and good ones can be had cheaply used.

Seems like it's something I should put on the back burner until I learn a bit more about the market there.Hopefully everything works out for you if you decide to invest in the Detroit market.

Fill it with water and turn all the burners on, place the pot on the whichever burner you want.

What shuts off the burner ?   

This approach is the last resort.Unless the property purchase agreement included an assignment of the architect's design contract that was signed by the architect, you have little leverage to compel them to perform other than throwing money at them to make it worth their while.Option 1 (best option): I would highly recommend sitting down with them, getting a new contract in which they are contractually bound to you and throw enough additional money at them to get you to their front burner.