I just suggested that because
@JMT was contemplating a drain at all and was worried about rust. I think a drain is a good idea as he would have to bail out the water without one.
I agree with simple being better, but they had reservations, So I was just adding suggestions to help with their concerns.
My suggestion is to feed the drain to the rear bumper as to alleviate the worry for rust. Then you said don't drain it where it can get onto other cars so I suggested putting a valve on it so he could drain where it is safe to not spray other cars. I thought my thinking was ingenious. I am curious to how all of this works out regardless.