Why not make the fleet slots a random draw so everyone who wants to join has a chance, not just the same few lucky individuals?
Set a deadline and give everyone 3 or 4 choices for slots that they can submit before that date, putting them into a random draw pool for that slot. After the deadline, just go through the slots and randomly pick someone from that slot's pool.
Part of the problem with carriers is that they tend to be slow and weak. They might not even suicide any more than other ships, they're just less suited to surviving the mistake and more likely to be noticed by players due to the circumstance (players assume they should always be in the backline) and confirmation bias.
Another part of the problem is that there is a lack of player control in the AI Tournament, which isn't an expected scenario in the base game, and the turn resets mess up the approach order of the ships, which in the base game it is assumed that the slow carriers will reach the battle slower and therefor tend to be in the backlines.
AI Tournament is a unique scenario not expected in the base game. Although AI could use some work, a large portion of the problems in the AI Tournament would be solved by compensating for the lack of player control and the messiness of turn resets.