Historic coal fireplace to RMH conversion

I live in a town that was built up in the heyday of coal, and the house I'm moving into has a coal fireplace in pretty much every room. My understanding is that coal chimneys are designed differently from wood-fire chimneys because of the differences in the burn - namely, that coal tends to burn more completely (and at a higher temperature) leaving no creosote. This poses a problem, I understand, with burning wood in these fireplaces because coal fireplaces are (1) often unlined and (2) far narrower.

But, hang on - burns hotter? No creosote? It *sounds* like a coal chimney would be perfect for venting a rocket mass heater, right?

So my questions are twofold: First, could a coal chimney be used safely and effectively to vent a rocket mass heater? Second, could a rocket mass heater be designed to preserve the historical character of coal fireplaces in an historic home?

My idea for design is like this: Move the original mantle and hearth face a foot or so further into the room, build a (plastered brick?) stratification chamber between it and the chimney. The idea would be to load the coal basket with wood, batch-box-style; the fire would burn upward in the normal fashion, turn back 90 degrees and then up 90 degrees; up through the insulated burn stack; and then down the stratification chamber and out the chimney.

My hope is that my doing this successfully I can make this technology more accessible to those whose homes have an historical character they want to preserve, like mine. I also feel that this technology is more in keeping with the spirit of these coal fireplaces than leaving them merely decorative.

Thoughts? I can sketch something and add it later to help with visualization.

Hi Mason;
This all hinges on the size and condition of the chimney.
First, we would need to know the diameter of the coal chimney.
Then, if it is large enough, you would want a visual inspection of its condition.
As far as retaining the vintage look, that might be difficult.
Hard to say without photos and measurements.
It will certainly be a challenge for sure!

There is a lot to learn about the different RMH designs and construction principles.
But most importantly, Batchboxes and all RMHs must be built to specifications!  (Changing them will void the warranty...)
If you try to modify one, it will not work properly.
If it does not burn hot enough at the core, you will produce excess ash and most likely creosote as well.
This will lead to increasingly poor performance.  
You would not be happy.

Mason, you mentioning in the first sentence of your post that there is a coal fireplace in virtually every room. Just a thought: could there be a fireplace in virtually every room minus one?

What you want is the idea of an open fireplace burning wood as fuel, looking like an old-fashioned coal burning device but with a lot of modern technology behind it. Unfortunally, that technology do start at the very front of a well-built Batchrocket, certainly not hidden behind a coal-heritage fireplace. Otherwise, it wouldn't be built to specifications and won't do what the technology suggests.

Said all that, here are the questions.
Are you talking about an open fireplace, or what?
In case there is a door, what size is it?
In case of no door, what's the size of the front opening?
What's the cross section size of the chimney and running to what height?

Personally, I did an open batchrocket in France, some years ago. It roared like the very devil and did warm a generously sized bell but its efficiency felt something... to desire for.
That brings me to a possible solution: a Double Shoebox Rocket #3. Most of the time called the Désirée, meaning the long awaited for. This is the shortest core in depth, burns upwards but... it's the hardest and most complicated combustion core to build of the four main batchrocket variants.
When done well, it would burn beautifully, but it requires a complicated door assembly. Never tested as an open fireplace, by the way.

Have a look at https://batchrocket.eu/ontwerpen#DSR. It's in Dutch, but Google Translate is very good in converting the text into readable English.
The whole of development of this core is published on an English language forum, namely Donkey's rocket mass heater forum. Have a read, and please consider all possibilities. If a properly built batchrocket can't be inplemented and you still want one, demolishing the coal hearth is the only option that's open.