If NASA decided that Butch & Suni would be flying SpaceX on their return trip, that would probably allow more aggressive testing of the Starliner's thruster sys

If NASA decided that Butch & Suni would be flying SpaceX on their return trip, that would probably allow more aggressive testing of the Starliner's thruster systems after it departs the ISS. In theory, the ISS crew could do a spacewalk or two before departure, to get a closer look at the problematic hardware. In practice - no time to plan nor train for that, improvised-at-best tools, and all the myriad ways that a flaky NTO/hydrazine fuel system could suddenly go very wrong - I'd be really surprised if they attempted anything.