I agree that going back to the abstract terrain rules would be a big help. Or at the very least have true "line of effect" to match true line of sight, as mentioned above, and adopt the ITC first floor rule. But being able to shoot into and out of terrain, but not through, is very simple to play and would solve a lot of problems. Everything else in this game is an abstraction; having terrain and line of sight not be seems misguided and unnecessarily complicated.
And does anyone actually really, really enjoy true line of sight in the "cinematic and exciting" sense? I just get annoyed that I have to get down and lean over the board and make a judgment call. To me it's just a huge hassle.
There's more arguments about that than anything in the game that I have seen. I too have leaned over and argued with other grognard and new cubs about what is and what is not seen by model X