Projections such as Winkel Tripel are great for showing a single, static image. But even if it could be interpolated into a conformal projection at close zooms, panning the map wouldn't work right. One option would be to pan the whole image, which would look very silly and make areas near the dateline unusable. The other option would be to try to re-center the projection. But if you're doing that, then essentially you've got Google Earth with a weird projection. At that point it makes much more sense to just use Google Earth.