yep...pool filter and drains would have to be modified. Only thing about raising the pump is mulm will collect at the bottom. May be you can connect a pump to the bottom drain to suck it out when needed.
Pools usually have a skimmer box as a safety to prevent draining of the pool. When the water level drops below the skimmer, the pump will suck air and cavitate, stopping the flow.
Another member in Texas did exactly what you're doing which turned out great. Check the outdoor pond forum. Unfortunately, he is on well water and the drought forced him to empty the pond
. He even got a heater on it.