I think my thoughts reflect others on here. Great idea but I suspect you would need a fair bit of capital to get this started and for your price point I do think it’s probably on the cheap side. Plus you need to factor in development, refinement, raw material costs and your time. As @SSPKali says is there a large enough gap in the market for bespoke face masks.
I hope I’m wrong and you can manage to do this and I think using thermoplastics would make it easier rather than using fibreglass type material.
If you were making these in bulk you might stand a change. I would probably make these as a high end low volume product then you might see some return.