Would love to see a mod that limits sideways/backward movement speeds for the PC and for humanoid NPCs. Would improve non-VATS combat a lot if PC and NPCs couldn't basically run sideways or backwards, and would make melee NPCs a little more threatening - currently I can pretty much run backwards and avoid getting hit by most.

Yar, I agree. Most NPCs can strafe my shots and avoid them easily.

That said, in FO3 I used a mod that did just that to the NPCs, and the player as well. I believe it was one of the XFO mods that did it, but it could have also been "Combat Enhanced" if I have the name correct.

Fook 2 worked this way as well.

However, it is a FOSE question, not really supported by vanilla scripts in NV. not that I've seen so far, anyway.

Arwen's Realism Tweaks reduces the speed at which you can run backwards (based on your agility), and it also alters combat behaviour a bit so that for example NPCs won't sidestep all the time to dodge bullets.