Hey there Spectacle Maker,

it looks like you've done your homework and have a good idea of what you need, that's great

To make it harder for you I'll disagree with Andy (though I'm not an expert at all) and say that something -like- a shapeoko could be good as a first CNC machine, even second hand. I have one and yes it's quite limited and sometimes not user friendly but if you find one that has a good working workflow it can be a very cheap way to start. Then after a few months you'll have a better idea of what you'll need. But because you're only machining plastic and don't necesarily want something super fast, even a small belt driven machine could work for you..

If you go for something 'overengineered' I'd make that overengineered in software, not hardware. Cause you don't need ballscrews or fast/strong motors cause you're not machining metals, but a reliable software that doesn't cause you problems and you can trust and work on other things while the machine is working would be ideal for you

I'd be interested in talking with you if you needed a bespoke machinery maybe for another step of the process (nice video you shared indeed) as I specialize on special purpose machinery. You mention it's hard to find tools for your trade so let me know if there's a solution you'd love to have!

cheers!