Mash Tun Question

Hey everyone, long time lurker, first time poster.

This may have been discussed before but I couldn't find it. I'm switching to all grain and had an idea for a sort of hybrid mash tun/biab approach. I bought a 5 gallon cooler and a 5 gallon paint strainer bag that happens to fit perfectly over the mouth of the cooler. I'm planning on doing a traditional single infusion with batch sparge, putting the grain in the bag in the cooler and draining the cooler through the valve it came with. I figure a stuck sparge would be nearly impossible. There's no manifold or false bottom, just the bag.

Any thoughts on this technique? I only do 2.5 gallon batches, so the 5 gallon cooler should have plenty of room.

It should work fine. Your finger will probably get tired of pressing that button to drain it though. Its very easy to pop it out and install a ball valve. If you're only doing 2.5 Gallon batches, you could probably just pour it out of the cooler into the kettle.