Sorry I mean I could write the asm in PIC not that I actually have, and if clocked suitably I'm quite certain would work just fine.
External hardware would be simple - but isn't what I want to do, and I feel that it must be possible to do this running a 16mhz clock?
I'm going to try and call on some programming help from someone who knows far better than I. Since the arduino has no problem generating a WS2812b data stream, or indeed even acting as a ArtNET node, I can't really see why it should struggle to do this, which is simply copying port data across, and potentially counting and snipping 'n' bits of data that passes through it. -I'm obviously missing something, or badly failing to explain!