Why mess with the balls? Seems like they would make cleaning very difficult and reduce the number of head that can use the waterer.

I use a couple Mira fount LilSpring 3100's (with windbreaks on the north or west sides) and they work very well with just the standard, preset, no-thermostat electric heater. The electricity use does not seem very expensive. The valves and floats are very reliable. Simple design. For 60 head maybe use the 3200?  Or go concrete. the Lil Springs are much less expensive and easier to install though.

As far as parts go maybe have a spare immersion heater around, though if you take them out in the summer even those seem to last a long time. The Mira fount valve is used by many other manufacturers and should be available locally.

Especially in MO I wouldn't think the ball type is worth the hassles and the electric use of the standard Lil Spring would not be significant cost item. Main thing with any waterer is to get it installed properly and airtight around the base. Also put a thermostatic heater on the riser pipe just in case.

I am a bit fanatic about being able to quickly drain and brush these things clean.

Jim