I can never leave engineering type problems alone. Ever. I know it's easier to design from a blank sheet of paper than dealing with real life variables, most times but not all, however I believe the below info is definitely doable. It could make a huge difference in overall ease of access to your driveway and it shouldn't require a lot of dirt to be removed. All units are degrees and inches. The overall length to pull this design off was 20 ft with only 1 ft of earth having to be removed within the first 15 ft. That's 1 day with a skid steer and a bucket. This isn't enough to require building retaining walls. I highly doubt it's enough to piss off the county and they probably wouldn't notice it at all. You could lengthen the base of this design to make it even more gradual, requiring less depth of earth to be removed. I only went after the first 20 ft. If you could double that, I'd bet only 6-8" in depth. The overall grade is still 15° at the end of the transition.