I like the nominations system, but it does have problems (as stated above by Blaze and Leigh). What we could do instead is hold exams for levels. Not like the written exams like the ensign and others similar, but rather field exams to show off your current skills. These exams could be held during sims when requested by an officer, the facilitator of the exam would accompany the crew during the sim, evaluate the officer and decide if a level increase is deserved. The criteria for the exam could be decided by the superior officers of the console