may I suggest a few air holes? After all, A fire needs air. A few 10mm holes 20-30mm up along the sides should suffice, say, about 6-8 of them just on the sides. After a few minutes of running science will take over. As the hot air rises through the flue it will draw cold clean air in via these holes. this will allow a cleaner hotter burn with far less smoke.
Oh and maybe a simple lattice for the inner base to raise the fire off the floor of the burner. it'd allow ash to fall away from the firewood and keeps the base of the burner cooler. Something like pic below maybe but with 2 front -back and 3-4 left-right? As I say, it's just a thought. Oh, and hypothetically speaking,,,, how much would one of these cost people if they wanted to buy one from you? I ask because,,,,because a friend(?),,,yeah,,, a friend wants to know how much it would cost me for one. I meant cost HIM, honest.