I can see how you could do it, but it wouldn't be a very effective one since it won't surface skim. It would also be pretty ugly. You'd have to buy a larger siphon tube and a strainer for it. Then figure out the biggest bulkhead you can put in the bottom of it, drill and install. You'll end up having to leave the motor on unless you can find a bulkhead that will fit that hole and use that for the drain.
I'd personally go to craigslist, Amazon, or Ebay and look for a fabricated one. I don't think it would be worth the aggravatio in the long run.
It is a violation of federal law to use this product in a manner inconsistent with its labelling.