Drive and tracking - I'd start stating that backlash is the foe.
We are adopting a brushed motor system from BBAstrodesign. The overall recommended reduction sits between 3000:1 and 10000:1.
It's a lot of reduction....But this is where the the dobson configuration nicely pairs with the friction drive concept. The set-up couples a stainless steel rail on a 1200mm diameter rocker with a 20mm h6 ground bar which offers a 60:1 no-backlash as a last stage. A compact low-backlash worm gear reducer for another 60:1 coupled with a 2.5:1 belt and pulley stage completes the drivetrain. Total ratio (60x60x2.5) is 9000:1. Please note that the motors come with a built in 10:1 gearbox that has few gear pairs - too much of backlash imho- conversely the belt will have a tensioner so that the main source of backlash is in the 60:1 worm-gear. Ideally I'd adopt an harmonic drive but it's pretty pricey and those I've found, come with a specced max 30' backlash which translate to 0.5arcsec on the scope axis - hopefully well manageable.
I don't see adopting clutches. That's a limitation but if the slewing is 3deg/s then we'll use a bit of patience.
Pic#1 of the mirror box with two main elements "pacman" - the rails is not present in this model version
Pic#2 The actual rails - 2mm stainless steel. 2 pre-rolled arches for the Altitude and 3 sections for the Azimuth bearing. A full circle would have set me off a fortune - and there's a trick for a smooth section transition.