I am in the process of restoring my ~1890's Queen Anne Victorian home and have a dilemma with what to do about the floors.

On the first floor, the original finished floor (fir) is simply installed on the floor joists with no other subfloor. A previous owner had installed an oak floor on top of this original floor everywhere except the dinning room where the original floor is still exposed: a nice (and decent but not great condition) inlay pattern of quarter sawn oak, ash and walnut.

The problem is that this results in a ~3/4" step up from the dinning room to all the other rooms that have this more modern oak floor installed over the original fir. There are 3 steps out of the dinning room: one to the kitchen, one to a bedroom and one to a dinning room.

We really hate the steps, and would like to replace the more modern oak floor with something else.

So the dilemma is how to handle the nice inlay in the dinning room, considering that we hate the step and that there is no subfloor.

I see our options are:
1. remove and replace modern oak floor, leave original dinning room inlay floor (leaves us with the steps we hate).
2. remove and replace modern oak floor and floor over the dinning room inlay (now we are covering a nice original piece of the home but eliminate the steps).
3. remove modern oak and original fir floor down to the joists, install new floor directly on joists (eliminates steps, but I don't believe installing a new floor directly on joists is a good idea. Also, I wanted to also put some patterns and inlays in the other rooms, and this option would preclude that.
4. Is there another?

Any thoughts or advice would be appreciated.

Sounds like the best idea would be to take out the fir and install a plywood subfloor over the joists. Then you can lay whatever floor you like. A new subfloor will also cut down on existing squeaks and noise.

Thanks for the response, but I'm afraid I don't see how that helps. This would still result in a step down to the original floor in the dinning room, which is what I am really trying to eliminate.

I wonder if refinishing the now covered floor is an option? My first assumption is that once you install a wood floor over a wood floor, that first wood floor becomes too damaged to restore, million nail holes and all.

If you remove the new oak floor and then the original fir floor you can order long length flooring so that you cross two joists, minimum, so that the flooring will be secure. I did that where a fir floor had been sanded too many times and was cracking at the top of the groove. We used long length Brazilian cherry where the lengths went to 13 feet. We used sub-floor adhesive when fastening to the joists, along with staples. The glue will hold 30% more weight. Brazilian cherry is very stiff. The long lengths have pretty straight grain and matched the fir flooring next to the entry after we stained a dark red color on the adjacent fir flooring.
Or you could take up the new 3/4 inch flooring and lay 5/16th inch thick flooring top-nailed like your "inlaid" flooring. It comes in 2-8 inch widths. A new pneumatic top-nail gun can be used to fasten the 5/16th inch thick flooring and this will match your height.

I get that everyplace except the dn rm is old fir covered with newish 3/4" oak, but are you saying the dn rm floor is oak with a inlay laid directly over the joists? I don't see how that would be possible. I've rarely seen oak T&G laid directly on the joists, but not with borders. My limited experience is that era house often had 1/4" thick strip face nailed oak floors and they sometimes had borders. But that doesn't explain your 3/4" offset/step. Could that offset be 1/2"?

Sounds simpler and cheaper to just recreate the old fir floor with a new one.