Is it worth keeping all the original gears on a vintage lock?

The short answer is you can absolutely keep the outer housing and those massive steel bolt workings exactly as they are. You don're not obligated to do a full shell swap just because modern tech usually means a complete replacement. Most of those huge cases, particularly the high-end display pieces from older eras, were designed with a substantial depth around the main strike plate, allowing for component separation. I worked on a similar antique cabinet last year and found that because the original mechanical components were so large, they actually provided a decent mounting structure for a smaller, more streamlined solenoid package. Instead of wiring a massive solenoid that would require a bigger hole and more visible conduit, you can install a low profile electromagnetic latch and mount the housing to the interior frame just behind the visible bolt mechanism. Then you run the necessery wiring down a discreet channel that was likely alredy part of the original case construction, often along the mounting screws for the display panel itself. It does require careful planning. You have to calculate the torque requirements of the original locking pawls so the new solenoid can trigger them without stripping the internal gear teeth. But mechanically, replacing the key cylinder and adding a modern electronic actuator is a standard preservation technique. The trick is minimizing the footprint of the new part so it doesn't look like you just bolted a modern piece onto a historical artifact.

If you are worried about weight, a lightweight, compact electronic strike actuator is the way to go. Avoid the bulky models designed for residential security because those have far too many internal components and are just overkill. Focus on models that are purely electromechanical and can be mounted flat within the cavity. This keeps the visual integrity of the case while giving you the convenience of a simple coded entry or remote access.

I'd try the boring option first before cutting anything. I had an old cabinet with a stiff original cylinder and half the problem was just decades of gunk in the keyway. A good flush out with cleaner and a graphite puff and it turned like new. Kept everything original and never looked back. If yours still fights you after a proper clean, you can usually swap just the cylinder core and have a new key cut to fit, and the boltwork never knows the difference. Electronics means batteries and a failure mode you don't want on a display piece anyway.

I went through the same debate with an old roll-top desk cabinet and ended up doing neither swap. The original key worked but you had to really force the bolt over, and what fixed it was a set of feeler gauges I had in my truck. I used the thin ones to find where the boltwork was binding against the strike, eased that spot with a needle file, and suddenly the giant mechanism felt smooth as anything.

Might be worth checking whether your keyway problem is actualy the lock or just the bolt dragging somewhere before you commit to electronics. These old heavy assemblies shift and swell over the years and half the time the cylinder was fine all along.

One thing I would add after doing somethig similar on an old china cabinet is to make the whole thing reversible. I kept the original cylinder and every removed part in a labeled bag taped inside the case, so if the next owner wants it back to stock it is all there. Also think hard about power before you commit, becasue drilling a channel for wire through hundred year old wood is a much bigger deal than people assume, and a battery operated option avoids touching the original timber entirely. My battery pack needed replacing about once a year, which I found perfectly tolerable.