Fantastic motif for a blacksmith! I never would've thought of that. How cool (or should I say hot) is that?!
Two thoughts on the imperfect circle---
1) leave it and he will try "forging" it in his mind and have pleasure in that
2) fix it with any of the aforementioned suggestions as a nod to the craftsmanship you each appreciate
Let us know his reaction, and when you've added more colors that you talked about!