If it were me I'd just get a bigger permanent magnet dc or shunt motor and use a contactor to turn it on. I doubt you'd loose much power through the hydrostatic drive simply because you need very little of the power to drive the wheels; unless you're plowing snow with it or something.
If you go the direct drive route you need a minimum of 2 reverseable drive motors and a controller, throttle, gear reduction drive, etc on each and 1 large blade motor. The cost of that is going to add up fast and then you still have to deal with getting everything calibrated to work well and buy your batteries. If you simply go with 1 larger motor of a type that needs no controller you can put your extra money in the batteries and end up spending a lot less.
If you go the direct drive route you need a minimum of 2 reverseable drive motors and a controller, throttle, gear reduction drive, etc on each and 1 large blade motor. The cost of that is going to add up fast and then you still have to deal with getting everything calibrated to work well and buy your batteries. If you simply go with 1 larger motor of a type that needs no controller you can put your extra money in the batteries and end up spending a lot less.
