I believe Tamiya's reasoning behind their suggested layout is that you should not need to remove the ESC in order to remove the motor (without removing the motor mount). Most of us do not seem to care about that and place our ESCs there for better balance.
I have the "huge" Novak GTB with a fan mounted in mine. It is mounted with the cables towards the rear of the car. I do use a low profile servo, Futaba BLS551, but I could still fit a standard sized servo. If you have a hard time making it fit, try turning your ESC 90 degrees so the cables face towards the centre of the car. I took some rough measurements off my Tamiya Volac BL2 (SXX TC with better looks
) that I use in my TRF201 and it seems that I could squeeze the BL2 in with the cables facing towards the centre of the 511 just behind the motor. However, if I would use the BL2 in the 511, I would still place it behind the servo.