Forgive me for posting a picture of an semi auto but I believe the controls on this one are unique and maybe we might see more makers doing this.
This is a Grand Power P11 Mk12.
This pistol has a cock and lock safety and a de cocker.
This is the only pistol that I know of that will allow you to shoot continuous double action just like a revolver without having to de cock each time.
So you can comfortably practice your DA and SA with the same weapon just like a revolver.
I think you are correct that the combination of SA cocked and locked (Condition 1 carry) and DAO options is unique.
However, there has been combined DA/SA de-cocker pistol and DAO "revolver" operation in the past.
The pistol on the top is a Browning BDM. It has a rotating mode switch that allows it to operate as either in DAO revolver mode, or in DA/SA de-cocker pistol mode.
It was developed for the 1991 FBI service pistol trials, but wasn't successful.
This was around the same time many police departments were transitioning from DA revolvers (some DAO, others not) to semi-auto pistols. The advantage was the ability to transition an officer or agent from a DAO or DA revolver to the BDM in "R"mode where it operated like a DAO revolver. The *only* training needed would have been the loading, reloading and immediate action drills.
However, things are a bit more involved in the pistol mode. The decocker is pressed down to decock the pistol, but then stays there, so you have to remember to press the lever back up to the"fire" position. In that regard it's a safety that operates backwards.
The decocker also functions as a slide release, which is nice as the regular slide release on it is small like the release on a Glock. However, you once again have to move the lever back up before the pistol will fire. The slingshot slide release method really works best for this pistol.
All in all there wasn't much if any savings in training, and most departments preferred to go with a little extra training for a conventional DA/SA de-cocker equipped pistol, or to just go the DAO pistol route. The end result was it was only in production for 7 years and they are not commonly encountered on the used market.
To be fair however, it also has the narrowest grip profile I've ever encountered on a double stack 9mm Luger pistol, along with the same narrow slide dimensions as the Hi Power. Size wise, it would have worked well for the FBI's intended concealed carry role.
The second pistol is an FN HP-DA. It was a DA/SA de-cocker equipped pistol developed for the second round of the M9 service pistols trials. It has a reasonably nice, light weight DA trigger pull and the de-cocker operates normally, springing back up after it is depressed.
----
This is all the long way of saying that a combination mode gun is only going to find acceptance if it also doesn't have any operational oddities or quirks in one or both of those modes.