Interested.
I was working on a similar thing myself but if this happens without me having to do any more work then I am about it.
Also, don't offer hotswap. Trust me, just don't. There's plenty of people that can handle that sort of thing après le mot, it would be better to find and direct people towards those resources rather than have that included in the groupbuy. It will not only increase costs for everyone involved but will slow the whole thing down.
Personally I wouldn't like the idea of my group buy dollars subsidizing someone else's poor life choices.
I'm assuming the PCB is going to be FR4, but what thickness? Also, what solder mask/finish are you considering for it?
If you really are going to offer barebones PCB kits, what's that QC process going to look like? Are PCB's going to be tested from the factory?
Who handles packaging and are you also sourcing materials from the same manufacturer that is assembling the pcb?