Do you think they would even consider riding back without a pressure suit?
In Shuttle days, there a concept for a pressurized survival bag. Not elegant, nor fun for the wearer but is one-size-fits-all. Also, once inflated, those smart-looking IVA suits do look stupid. You can find an example in the suiting-up room before the Starliner crew launch. Has anyone seen the SpaceX suite inflated? It looks like a good argument to switch to the EVA one... or just a bag with a face-plate as I suggested.
Or perhaps they wouldn't even agree to consider that, unless it was an absolute dire emergency?
I think they wouldn't agree. Its probably better to take a couple of month's holiday in orbit and wait for the SpaceX suits.