Fat bike tires will NOT fit on a bike that isn't specifically designed for it. Fat bikes are designed around wider hubs and bottom brackets to have clearance for the tires. There have been some full suspension fat bikes by Salsa and Trek ( and some custom manufacturers),but they stopped production a few years ago, you may be able to find one used . A lot of modern fat bikes come with a suspension fork. You could buy one of them and get a second set of 29er wheels built on the correctly configured hubs to swap out for summer use.