I was annoyed by this problem so much that I made a program specifically for this - to be able to scroll dialogsand select dialog options with anything (by using mouse wheel and keyboard). It's called Aurora Dialog Enhancer.
Hopefully someone will actually find this useful besides me, because it's just become many times more convenient to play GI.
You can check it on GitHub: https://github.com/DigitalE4rth/AuroraDialogEnhancer