Whether or not this is even possible probably depends on the hub. It might be more than 130mm wide without spacers. If you aren't removing the same number of spacers from each side, you'll need to re-dish the wheel, unless you can live with it being 2.5 mm off-center. Otherwise, I suppose it could work.
You could consider getting a 29er front wheel and using rim brakes with your favoring road wheel in the rear. Rear disc brakes are almost always overkill.