I have a two Prusa MK3Ss. I also have two Prusa Mini clones (Fysetc kits) that I bought, as most everything I print fits in the build volume. I don't like the cantilevered design, as it's too easy to skew an axis, and I want parts from any printer to fit together.
So, I'm considering using the Mini parts to build an i3-style printer. I'm not sure what to do for the z-axis, though. Would it be better to get a second motor/lead screw for the z-axis or to run a belt from the one z motor to a second lead screw? For the second motor, I'd try to get the same motor/lead screw, so they match. Any issues wiring the motors in series and then ramming them against the tops to sync, like the MK3S does? For the belt option, I'd mount the motor at the top with the belt pulley very close to the motor and the end of the lead screw unsupported. I could potentially design a motor mount with a bearing to support the lead screw right after the pulley. The Mini z-motor has a 311 mm lead screw, which should be plenty long to get 185 mm of z travel, even with a belt system.
