Sound like a good plan. My advice, go as big as you can, you'll regret it if you don't. I went with a 30' X 60', with my woodworking equipment and projects spread out all over, wish I had gone 40' X 60'We've got it planned as 24' x 50' (over 24' wide needs extra bracing and adds 6k to the cost.) In my mind I have one bay for a 4 post lift to store 2 cars (Dodgey and my Vette). One bay is a 2 post lift, one bay is a "dirty" work area, and one is a man cave/tool storage/clean work area.
I should have gone with insulation too but, I already have ~$45K in it and I did all of the electrical myself. It adds up fast. I do have 3 roof vents (not the garbage whirlybirds) which can be opened and closed from the floor with chains going to them. Got 2 - 16' X 10' industrial grade garage doors with electric openers. They help quite a bit with cross ventilation too. HTH