Thanks for the suggestions.
I've looked at the LiDAR Lite V3 before but a little put off by the price (I'm not suggesting they're not good value though). I will probably try with cheaper components at least to begin with just to see where I can get to since my current goal is more around my own learning. I realise that this does seriously limit what the end product is capable of and I don't want to be doing the cheap basic versions forever.
Yeah I will probably go for the Teensy in the near future. I have an RPi kicking around (never used before) and wanted a project for it but I have some other things in mind for it now. Later on I may add it to a Teensy based QC as you suggest.