Forty-five-degrees is a ridiculously steep angle for ramps. For more realistic ramps, they should be between 5 - 15 degrees. Though, I think for the purpose of stability issues the angle would ideally be 11.25 degrees so that every four blocks will (theoretically, I hope) snap to support pillars.
Adding angled and/or curved ramp corner pieces would be nice.
While I agree with you, the problem with these kinds of things is the sheer amount of “support pieces” that any “additional angles” requires. It’s the same reason we don’t have a forty-five degree “corner foundation” either. Now you might say you’re fine with just the ramp, but there’s plenty of people who won’t be.
For an example, just see the crazy proliferation in roof pieces just to properly roof the options we do have (which is great, by the way!).