I mentioned a while ago that I was converting my CGE-Pro to SiTech motors and controller - and I will provide here a short summary of how it went.
I am now using a CGX-L and the conversion of the CGE-Pro was mostly to give it new life and also just as an interesting project to see how it would work. As it happened, a friend was suddenly in need of a new mount, so as soon as it was working I lent it to him and he has been using it ever since.
The conversion makes direct use of all the switches on the mount: for homing, axis limits, and the PEC index with no additional electronics. I just needed to make simple connects to connect the original wires to the SiTech controller. The controller is set to receive those signals with no pull-ups or anything - and the software can be configured to use them directly.
The main challenge I did not expect ended up being mechanical. The motors have screw holes that are directly compatible with the original motors, but the gearbox and electronics connector on the SiTech motors is on the wrong side and cannot attach directly. This means either machining a whole new way to attach the motors - or to create a bracket to offset the motors and drive with a belt. I chose the belt approach - and for the bracket a friend designed and created a 3D printed plate with holes of the right spacing.
Getting the orientation and spacing of those holes was quite challenging and required some trial and error. The end result shown below ended up being too tight and close - but it seems to work fine. But if anyone does this themselves I would use a longer belt so there is less conflict of the motor with the worm bracket. I was concerned about possible flexure of the 3D printed plate, but it is thick enough and short enough - and has some reinforcement - that I think it is fine. But if you have a machine shop aluminum might be better.
I chose to use a 1:2 reduction pulley to match the original spur gears - but you can use any ratio you want and configure the SiTech driver appropriately. The pulleys and belts are from sdp-si. The shaft on the motor and the shaft for the worm appeared to be English in one case and Metric in the other - so for a tight fit I got the exact one for each. I forget what size they were but I can look it up if there is interest.
The software and documentation for the controller and software are somewhat idiosyncratic and you may need to look in multiple places - but it does make sense and there are tons of features. Once you have it configured properly you shouldn't need to alter it. You end up with a full software suite for building pointing models of the mount using the same PointXP software that comes with Mesu mounts.
I wasn't able to test guiding and tracking in great detail - but from all I could tell there was no change from the original CGE-Pro. The ASCOM interface works fine for both control and guiding.
Here is a picture of how it looks - showing the adapter plates and pulleys. Note that the motors are oriented so the wires feed out more cleanly in a downward direction. There are a few wires leading to each motor and I wrapped them in a cable housing that is thin and flexible.
Overall I think this is a good way to get more life from a mount that may have problems with motors or controllers but is otherwise mechanically fine. It isn't cheap since the controller, motors, and handcontrol end up just over $1k - but in many ways it is an improvement over the original.
I'm happy to answer questions if there are any. I assume a similar approach would work for other mounts.