By reducing the diameter of the discharge line from 2 inch to 1/2 inch the volume of water moved will collapse.
The frictional losses will be so great water may not even get out the end.
Pumps and discharge lines are matched for efficiency.
Depending on the volume you need to move, the ram pump over a 24 hour period will shift a lot of water.
Perhaps look at the cost of the different types of pipe.
Poly irrigation pipe is long lasting compared with some lay flat hoses.
The difference in cost may justify the better pipe.
A smaller capacity pump maybe worth considering, but if you are using a generic fire pump, it will need to run at a slower speed.
Do you have the flow in the brook to
feed a 2inch pump?