I don't have much experience with brushless motors, is an esc the only way to control them? As in a brushed motor for a specific voltage could be turned on/off with a relay switch, no speed control needed.
With the esc's that are available nowadays & the choice of radios too, the rpm of the motor can be preset to whatever speed is recommended.
There are voltage regulators from Castle Creations that could be implemented into the rc system as well to control motor speed of any brushed/brushless motor.
Inline pump & motor vs stacked with a belt drive, space availability will decide that combination necessity... good to have options.
Personally, every hyd system I do in the future, the pumpdrive motor will be governed with an esc and that'll do alot to control unnecessary heat issues of oil flow running when it doesn't need to or atleast not as fast.