This may work in normal times, but the border remains closed now and likely will for several more months.How far are you from Michigan? Ontarians quite regularly purchase cars from Detroit and Port Huron area dealers. I'm not sure if Mach E is on the approved list yet, but aside from cheaper prices, pretty much anyone in Michigan will participate in X-Plan (not necessarily for Mach E, though; you'll still have to call around). And no, the warranty is not invalid when you cross the border.
Lots of newspaper stories lately about snowbirds in Ontario having their cars shipped across at Buffalo (border not closed to commercial trucking), then flying in a helicopter from Hamilton/St Catharines to Buffalo. Canadians arrive at Buffalo airport private terminal, pass thru customs, hop in their waiting car, drive to Florida. Newspaper quoted $1200 CDN for 3 passengers and $700 CDN for the auto transport across the border.Not a bad idea but I think with COVID closing the boarders I don’t think that will work.