There's nothing stopping FFG from imposing a per-ship time limit. Say, 3 minutes per living ship - obviously, in scenarios where there is a 2 ship list vs. a 6 ship list, both players would just operate at the highest count list present at the board.
Although good in theory, you can pretty much guarantee that players would abuse it by trying to run the clock out when the're winning. Personally, I think it's a good idea, and I don't know why they didn't impose a time limit in the first place.