We did a remodel of our house garage when we had to strip the ceiling to have access to the floor and walls of a bonus room above. Couldn't keep it cool in the summer so had it foamed. Not being a big fan of sheetrock in a garage I also stripped the walls since there was some damage after 15 years of use. I went to Lowe's and found some 4X8 sheets of siding with a woodgrain texture and grooves to make it look like planks. It is lapped on both sides so you get a clean joint. I painted it with a good exterior semi-gloss and after 2 years it still looks like the day I did it. I sheetrocked the ceiling by the way.
The sheets are a fiber of some kind but not MDF, I'm pretty sure. I didn't pay any attention to the fire rating if there is one. Another issue is the 4X8 size. I'm sure you have taller walls than that so if you are going for a look you would have to deal with some seams that join the top and bottom of the sheets. The last issue would be cost. Quite a bit pricier than OSB but if you use sheetrock and finish it out the cost difference might not be so much.
I also have a separate shop/rv garage that required some fancy footwork to get approval to build. It had to match the house which included some bricking and siding. I separated my shop from the rv garage with a dividing wall. My shop walls and ceiling are also covered with 4X8 sheets of exterior siding but it was a plywood product from 15 years ago. Since I didn't want to have climate control in the rv side I just have exposed studs and rafters.
One other thing and then I'll quit. I hope you can get water, electric and a sewer dump to your new building. I have 50 amp electric and the sewer dump in mine. I have an outside faucet on our house that is about 50' away from the garage so I use it for water. The city inspector only allowed my dump after I changed it from a dump to a 4" cleanout. Sure makes it easier to travel not having to worry about finding a dump, er cleanout, along the way.