I was researching this option (Windsor/Detroit) thing and came across a term Permanent Resident Commuter Status (US Green Card C2) - which allows one to live in Canada/Mexico and to commute to US to work.
The time a US GC holder is on a "commuter" status does not count toward naturalization.
I think this can be a way to go for someone who wants to continue living in Canada, accumulating days for citizenship - but works in US on "commuter" status.
If one day a person decides to live in US, the commuter status can be changed to a regular GC card (and naturalization clock would start).
I think a "commuter" status US GC should not affect Canadian PR card renewal or application for Canadian citizenship. In fact, it might help, as it explains the employment situation and that it is likely that the person lives in Canada if he/she opted for commuter status. Its an official "give up" on physical US residency.
Does anyone have any additional info or opinion about this option?