I would go with power venting the oil burning furnace and venting the coal appliance into the chimney. In the long run it will end up costing a lot less in reference to the electric bill. Also, with the coal burner on power vent you will need to install an uninterruptible power source as a back-up to keep the vent running if there is a power failure to eliminate any possibility of products of combustion entering the living space. This is not needed with a power vent on an oil burner, as the burner will shut off when the power goes out.
I was going to power vent my coal stoker out the cellar window (I only have 1 window that was a larger opening that was used to chute coal into the cellar years ago). I decided to vent the coal stoker into the chimney.
I have a very thick fieldstone foundation here.
With the proper coal burning set-up the oil burner will never run. There are also coal burning central hot air furnaces available, I'd consider one of them if you have the room in the cellar and the cash to buy one. I'd stay away from combination units (that burn multiple fuels such as coal and oil), as they are known to be quite inefficient.
As far as this being complicated, yes it is. But once you sort it all out it becomes more understandable.