I get the appeal of the trials as they are. It really fits Americans' idea of "merit." And certainly - you win (or place in the top 3) and you qualify is as straightforward of competition as you can get. On the other hand, you could argue that there are other forms of merit - showing consistency over a longer period (one year, 18 months, 2 years), best times overall, etc.
I could get on board with top 2 qualify at the trials, 3rd is a wildcard based on the past 1-2 years. As long as all the competitors know the selection process in advance. But, I highly doubt that will ever happen. The selection of the wildcard could get messy. If it did, I'd imagine that in a lot of events the top 3 trials finishers would still be the team. The wildcard should only really be used in situations such as where a top athlete is injured or otherwise unable to compete at trials. But, again, I doubt it will ever happen.