Kinda old school, but Rule 1100 aerators move a ton of water one way for like $35, draw a small amount of current, won't burn up if run dry, and you can buy them with replaceable motor cartridges. They don't block reverse flow, so you may have to take measures there, and yes, they do need to be mounted below the waterline (fill) and sac drain (empty). My Rule fills a 750-pound sac in like five minutes. Four Rules on your setup would be a really quick fill and empty and could be had for $150 with a spare motor. The Rule website will show you how to orient them to reduce the chance of airlock.
The good news is that this topic gets killed every five minutes or so on wakeworld, so you've got lots of info and opinions at your fingertips.
Make sure to take some pics for us, though - everybody loves to look at ballast (and stereo) installs!!!