I agree with your request in general, but I don't agree with your example.
I hate to sound unsympathetic, but YOU are the one who wasn't paying attention, YOU are the one who didn't double check your role before locking in, YOU are the one who didn't look at chat until things were about to load. How the game works made it possible, but you almost certainly knew things work that way before you even queued. Somewhat extreme example, but how well do you think 'I wasn't paying attention, it's the car's fault because it didn't stop when it needed to' would hold up as a defense if you accidentally run someone over in a car? In both cases, it is absolutely your fault, not the game's, not the car's.
Now, that all said, yes, I in general agree that it should give preference to what role you were selected for first (provided you didn't get autofilled), but keep in mind that part of the reason it doesn't is to try and get you into a game as fast as possible (you've already sat through at least 3 pick/ban phases, most people really do want to get into a game ASAP at that point).