If you completely eliminate the oil pump you will loose the oil supply to the water pump/ oil pump drive shaft bearings.
IMO...for trail riding I would NOT eliminate the stock oiling system as it works very well when it is in proper repair. After a rebuild I would ensure that all the oil lines are connected, not leaking, and that the line check valves are pointed in the right direction.
Ensure that the oil pump cable is adjusted properly.
For the first tank I would premix about 50:1 until you have established that the oil pump is working and that you are using @ 1 litre of oil per tank of fuel...then you are good to go!