Magnolia44, If you do find it possible to insulate and re-stucco, Make sure the R value of the insulation will be high enough to warrant the cost of the work. I would think that in Denver, you would want at least an R-25 rating for your walls, to have an efficient living space, you would also want the ceiling or roof to have R-30 or greater. Check with manufacturers for specifications for your area. The next issue that would need to be addressed is the support of the additional wall, and would it be protected by the existing eaves of the house?
You would have a very interesting house, with nice thick walls, reminiscent of castle walls, an could have the windows mounted to the outside, so that you had fantastic window seats for whatever in every room!!!