Interesting problem. You may be able to 'drop in' a 240 VAC deWalt router IF the power relay is rated for it (or replace power relay if not). Then you only need worry about the arduino and steppers. I'm guessing they've already given this matter some thought, back in the mother ship.
I'd skip the transformer if I were in your position. Heavy and crucial, just one more thing to keep track of and possibly drop on your foot. Whereas changing the operating voltage is a one-time hassle.
But the more I think about it the more I suspect ShopBot will be able to accommodate you with a 240VAC machine.