Just wanted to mention this here as some people here seem to be after something similar:
I am working on a expansion bay module that will include a OcuLink (4i) port, mini DP in (as soon as I can find a fitting connector) and 3 extension card slots among a few extra bits.
Might be interesting for those that were/are interested in a OcuLink module including USB C.
Im not including PD input via the extension cards as that a) would add a lot of complexity and b) the interposer only allows a max of 80W for input power, which isnt much at all considering the laptop itself can be charged at 240W…
Thread for the module Im working on is here: Expansion Bay Module for Extension Cards