Different weapons should have different ranges. Real Players and NPC'S included
For example Mechanical torpedo's should have the longest range and accuracy because they have guidance systems and do not depend on the ships power systems or any rank to fire.
Energy based weapon's range should be regulated by weapon type.
Energy based weapon's damage should be regulated by 1st weapon type and range.
Pulse, Cannon and energy based torpedo's Should require some "Player skill" for Accuracy and damage. In essence you are firing a ball of energy with no guidance system at a moving target.........
Really there is no logical reason why a lieutenant should not be able to use a mark 10 weapon. It's all about available slots/hardpoints and ships available power to fire each weapon. If your a Lieutenant and your ship power can either 3 mark 1 weapons with a short recharge or 1 mark 10 weapon with a long recharge based off of available energy then you should be able to choose how you set your ship up. This idea gives great promise for variety in strategics.