This really wouldn't help. If a wingtip just scrapes the ground, it won't send the airplane into a spin. To spin the plane enough to cause a crash, the wingtip would have to plow into the ground pretty hard. This will result in a crash even if there is a wheel. You might think that a wheel would be less likely to dig in and catch, but the flat bottom of a wingtip will skid on a runway very well. The reason some airplanes (like the U2 spyplane) have wheels on their wingtips is to prevent damaging the wingtips when they scrape the ground, which happens routinely. (U2's have very long floppy wings.) Airliners almost never scrape the ground with their wings, so it isn't really an issue.

Sparks at the wingtip are unlikely to start a fire because there is nothing to catch on fire way out at the wingtip.