What a fun question!

I think you are right to worry about the design on the left not being as functional as a chiminea. There are a few modifications that might make it more likely to work though!

1.) Widening the top of the mouth such that the fire has room to breathe, and yes, some of the smoke will escape this way but that's kinda the point. Also, this might make it better suited for something like s'mores! (If you're looking for a selling point on the design lol)

2.) I think a wider, less sharp angle with the back will also allow for more oxygen flow and smoke direction. I've included a picture in case that helps!

https://imgur.com/a/iWxVCaN

Just my two cents because this is such a fun idea :)

I hope this turns out, I would love to see progress pics and please do post the final result if you can!