Opening Cab Doors on the 1/64's

No.

First of all, with opening doors, you get unrealistic, out of scale door seams that look terrible. Check out a Road Champs 1:43 car and see what I mean.

Second of all, it would mean additional tooling for Code 3 to manufacture the door hinge mechanism, and they're already too expensive for the most part.

Third, if they make opening doors, then they're going to have to begin to detail the interiors. Again, that costs money, to create a more realistic interior, and to paint seats, dashboards, etc.

Leave them how they are. Don't fix what ain't broke becuase the moment you do, it breaks worse than your can ever fix.

+1 to all that.  I'd go into further detail, but rescue42 already hit the high points.

It's not a terrible idea, but like the concept of working lights in 1/64, the chances of a massive fail are too great of a risk at this point.