Why not just buy an ebike that comes with plus-size tires? Plus-size is industryspeak for 3-inch (or thereabout) tires. I have one, a Haibike AllMtn Full Seven Plus, meaning it's a full suspension mountain bike with 27.5 wheels and 3-inch tires. The larger wheel (compared to most fat bikes' 26-inch wheels) is also an advantage.
I believe you will find many ebikes with plus-size tires, not just Haibike.