If price is your concern get LEE dies. Their dies are less expensive and are every bit as good as all the other more expensive dies. I've used Redding, RCBS, and Lee for over 30 years and some of the most accurate ammo I have produced for 30-06 and .308 has been processed using LEE dies. Their die sets also come with a shell holder. Some other sets require that you buy this separate, thus increasing their already high price. Midway USA has the Lee pacesetter die set for sale at $22.
ABSOLUTELY NOT NO WAY.
The neck opening on a .30-06 is about .306" after resizing it to seat a .308" diameter bullet
The neck opening on a .270 is about .275" after resizing it to seat a .277" diameter bullet.
No possible way to resize the neck on a 30-06 case with a .270 die and be able to seat a bullet into the neck.
The .270 is also a longer case with the shoulder set closer to the mouth then a .30-06 no way.
I think you have a novel way of doing this, however, for a semi-auto rifle, you need to make sure you are full length or small base sizing otherwise you will have feeding/chambering issues. I think your approach may work, but probably not as well as you might hope. I don't know if you have a few live rounds available to you, if so take one, pull the bullet, measure OAL, and the body just below the shoulder resize, and compare results. you can also cover the case in sharpie and resize, which will give you an idea where the die is touching the case. I think the real proof here will be in chambering some dummies and maybe trying it out.