I think what most of us have done is to certainly to have two electrical
pumps, one that is working and one as a spare, but not fitted.
Making sure that what ever the make of pump, the fittings are the same and that it is ready to easily slip into the outlet hose without any fuss, and that the electrical connections are the same for both pumps.
Due to the easy access of the electrical bilge pump in the engine room, it is not necessary to have two electrical pumps fitted at once.
If you did have a problem with water flooding your bilge, your manual bilge pump would keep it down until you fitted the spare pump.
The manual bilge pump is designed to use the cockpit table leg as the lever so that anyone sailing alone can work the pump.