LOTS of electrical outlets; walls and overhead drop downs.

Lots of light, skylites make for good natural light (though that would be more useful in the paint area), though in your climate might be tougher on heat control.

A floor drain/wash area would be nice for a warm area in the winter, cooler area in the summer.

I vote for the painted floor too.............MUCH easier clean up. I used the Rustoleum kit in my shop six years ago and it's still going strong.......great value for the price.

An I beam overhead with a rollling hoist would be real handy.

Some form of exhaust venting, a tube system like commercial shops have would be the bomb.

I like the roll up type doors (the small sectional type that form a "log" when rolled up) on an operation this size, powered would be a bonus touch. They don't intrude as much on the overhead space, and don't block light (remember..............LOTS of lights).