Sounds like an idea, except there's only one problem: MOLES won't eat your lilies, not any part of them, neither the bulb nor the foliage. However, VOLES will, but they travel above ground on the surface, both winter and summer. VOLES generally attack lily bulbs in the winter by digging down through the old stem hole in search of baby stem bulblets and bulbs when their normal food supply is short. In the summer, when other food sources are abundant, they are seldom a major concern, although they will occasionally chew a budded stem off so they can get at the buds to eat. On the other hand, think of ground MOLES as somewhat of a friend; they aerate the soil a little with their underground tunnels and feed off underground insects, some of which can be harmful to your lilies.
Concerning your idea of using a pool with many drain holes, remember this: Regardless of how many drain holes you have, in the winter if they all freeze shut, you end up with a pool of mud that freezes and thaws--the ideal condition to end up with a bunch of rotten bulbs the following spring. Depending on your winter climate, this may be a major concern.
