Our team has co-captains (2-3) and subteam leaders for our 4 subteams (mechanical, electrical, programming, and PR). They don't have to be the same people, and their responsibilities are very different.
Check out the Agile development and
Scrum. It's a process designed for short work cycles and rapid development, and can pretty easily be adapted to a FIRST environment. We have 1 week "sprints", with clearly defined design, prototype and construction goals for each week. The captains act as the product owners, reviewing the work regularly (the end of every meeting) and ensuring we're meeting our goals (reevaluating the schedule, if need). Our development teams are small (3-7 students), with that single leader acting as the scrum master. Decisions are made rapidly by the best person for that decision, which more often than not is NOT someone in an official leadership role. After all, you want technical decisions made by those most familiar with the product and its design, not someone whose focus is elsewhere but happens to have a fancy title.
Most importantly here, I would highly recommend making any organizational changes with the full knowledge and consent of the entire team. Have a meeting, raise your concerns, and talk with them about how you want to resolve those issues. Get them on board with the changes, otherwise you'll likely hit some resistance along the way that could make the whole situation unpleasant.