This is the front of the garage. Please excuse the crappy editing.
My idea is to extend the left side bay about 8 ft.
To try and break up up what might look really boxy and also tie into the look of the house I'd add a gable roof over the existing garage and then a smaller gable over the extension.
Barely visible are the cable (bottom wire) and the power (upper wire.)
Here's another shot of the roof showing the power and cable lines.
The challenge here is that getting 12ft of clearance between the new roof deck and the power would be very difficult as the mast on the house is power line now is almost level with where the line is on the pole. So the only option would be to move the meter to the front left side of the garage and then feed to the house.
There's a gas line running down the left side of the garage so trenching to get from the garage to the house could be tricky. I don't recall what separation is required between power and gas services.
Edit: looks like same trench is fine with 300mm of separation.
This would be a big undertaking, the vast majority of which I'd have to contract out. As a WAG it would likely run $20,000+. The floor space gain would be pretty minor; under 80 sq ft and the potential for some attic storage because I'd keep the existing 2x8 roof trusses as the bottom chord of new rafters. I'd also get a fully insulated shop whereas right now I don't have ceiling insulation.
The "easy button" is just to build the extension and not fuss with the roof. Same 80 sq ft floor space gain. Less cost. Potentially looks like crap.
The easier button is to get a Bike Barn for the moto and get it out of the garage. I had one of these before and they are really slick.
Also an 80 sq ft floor space gain as I'd reclaim the area where the moto is parked now and the full 20'x20' garage would be shop area. Smart money says this is the way to go.