[Astronouth7303]

If you want any decent control of the turret (or any other mechanism), you need to put sensors on it. Period. Potentiometers are pretty small. Surely you can find someplace around the turret that isn't crowded out. (I've never seen a robot that full.) If this is a problem for you, I think you're doing something wrong. (Also, limit switches of some kind at the ends of travel would not be out of order. Partly for calibrating the "pots", mostly for keeping the bot from tearing itself apart.)

What you're suggesting is to basically "dead recon" the turret. Yes this can be done, but as soon as a robot runs into whatever is attached to the turret and turns it, you're hosed; all your movement will be off. (And heaven forbid you don't put the turret in the same place at the start of every match. It starts off wrong, then.)

Any closed control loop (something with a sensor) will compensate for such movement.

All of these are important factors in FIRST, especially this year, because you can't always see so well if your robot is on the far side of the field.

Bottom line: yes, you could do it, but it is far more worth your time to squeeze in those sensors.