You have a .270Win and if you can shoot that rifle, you can take everything up to dangerous bears. If you are willing to only take shoots within the limits of your .270Win, you can certainly take elk and moose with that rifle/cartridge combo. To jump up to 30-06 is not enough reason to get a rifle, considering that the .270Win will do just about everything that a 30-06 will do and will shoot flatter then does a 30-06. The 30-06 will get you into heavier bullets, but with the newer premium bullets, you may never need heavier then 150gr.
The way you phrased your question, you may simply want another deer rifle. Okay, in that case, I'd opt for the 300WSM, over the 30-06. Again, you were talking strictly deer and wanting a three rifle battery. Okay, third piece a .243Win. The .243Win can prove to be a little light for deer, but if you get good with a rifle in that cartridge, it can be fun to pick shots on white tail deer and pronghorn sized animals and go for one shot neck shots. In terms of tack driving accuracy, you can get it from a well set up rifle in .243Win.