I think that the biggest worry would be sunlight melting the wax off.
Other than that, it seems like a grand idea, the wax coating would be fairly
water repellent at least at first if not all the way through a season of growing.
It seems the factor would be erosion of the wax and there is only one way to find out for sure.
Give it a go, at the worst you would notice the wax turning white and eroding and then just setting it in some other container might be all that is needed.
Redhawk