I have always wanted to replace the mount on my prusa clone to something that gave me a larger usable print area and a much more stable platform for a Z probe.
So here it is... This mount balances on the X axis rails. The motor is behind and the extruder is in front of it. The only catch is that you have to use a motor with a minimum of 22mm shaft. Unfortunately most thin motors have 20mm shaft despite the distributor's claim of 22mm. They usually add the 2mm base platform thickness .. but some motors have true 22-24mm shafts like the E3D titan motor. So check the design diagrams and not just the params.
With this design the plane of extrusion is very close to the plane of the X axis, so if you use a touch based Z probe like the precision piezo, you get a better precision because the touch force mainly goes to the sensor and not to the rotation of the X assembly. This rotation gives a huge effect ... some of the other piezo sensors are even set up to trigger on the rotation and not the touch itself.
I included a set of pictures that show how to assemble. I used a Titan extruder, but technically, you can use others too. In the titan extruder the setup leaves a bit of space in front of the motor shaft so I used a screw backwards there to hang additional things to the assembly like a cooling fan.
The design uses brass sleeve bearing. There are 2 common types (IDxODxL): 8x11x22mm and 8x11x30mm. I'm including the design for both.
On these photos I used my piezo mount found here.
in fact I'm using some of the same photos.
0.2mm .. but 0.1 will work better