Honestly, what I want is this:
For Legacy, a button that guarantees that the character will forcibly align with the camera (face the same way as the camera) but have legacy controls otherwise. Think right click to align with camera, left click to free spin (or vice versa). This eliminates the biggest disadvantage of legacy (You cannot rotate your character without moving your character.) Likewise allow a toggle so strafe left/right + back isn't slow.
For standard, I would like the option to press back and have it behave like legacy (run backwards). I would also like the option for the character to always forcibly align to the direction the camera is aiming if right click is held without wiggling the mouse (so casts while you run out don't cause you to run at the boss until you wiggle the mouse).
You might be asking what the difference is and the answer is clear. I love standard for the ability to rotate my character without moving, which is fantastic for casters, but I like legacy for the omnidirectional gameplay and camera controls. These 2 options allow the option of tuning your favorite control scheme to behave more like the other but so you have comfort and the desired best aspects. And nothing makes me hate Legacy more than being unable to face my character without moving. It really hurts caster gameplay a lot.
To expound on this: camera controls are probably the best actual control scheme design of a player in terms of movement, but because facing mechanics are so important, we need the option to force a facing quickly and effortlessly without moving the character. Movement should override facing with the general exception of if a movement is valid and a facing can be maintained, it should allow it (strafing in legacy basically) but quickly backpedaling is very important for mechanics and simplifies complex gameplay. Making mouse 2 always turn the character without wiggling the character would be mostly great (as an option), especially on standard if it instantly overrides auto facing so you can fire spells and then instantly turn away without movement being impacted.
But because Legacy makes facing so difficult to work with, it means any fight with a strict facing mechanic (directional teleports/forced movement/vomit mechanics) is arguably harder to optimize for casters while not exactly always being easy on tanks/melee/phys ranged. Meanwhile, standard has the clunky and awkward movement that people hate about it after trying legacy with strafe, but when you want to really optimize facing, you just can't. It's not possible. Ergo, allowing standard to have better movement options like legacy, and legacy better facing options like standard, would help bring the 2 movement styles together and make controlling the character precisely easier.