The bypass thermostat does just that. It causes the coolant to bypass the radiator by redirecting it back into the block allowing for quicker warmup of the engine (and heater if needed). The electric fan (not moving at all until preset temp. cut in) would make the bypass less neccessary, since the cooling of the radiator is diminished as compared to the mechanical one at lower temps.(the viscous clutch still has SOME coupling at low temps). It really shouldn't matter if you keep the bypass thermostat with an electric fan; it just become a bit (small) redundant.
A wide enough spread between the on/off set points on the sensor for the electric fan would prevent excessive cycling. (much like our A/C compressor cycling).
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)