Even professional traders behavior is swayed by things like fluctuating testosterone levels. (Not that I know how to compensate for this!)

Bring some women to the team. (Yeah, that just changes the problem to a harder one: Where to find enough women rationalists interested in finance?) Or have multiple men on the team, and let them decide through some kind of voting. This would work only if their testosterone level fluctuations are uncorrelated. You could do some things to prevent that, e.g. forbid them to meet in person, and make their coordination as impersonal as possible, to prevent them from making each other angry.

This sounds like a huge complication to compensate for a single source of bias, so it needs some measurement. If this could help the team make millions, perhaps it is worth doing.

Economic irrationality invalidating the libertarian free-market ideas

Maybe irrationality could be modelled as just another cost of participating in the market. There are many kinds of costs which one has to pay to participate in the market. You pay for advertising, for transferring goods from the place they are produced to the customer, etc. Your own body must be fed and clothed. Irrationality is a cost of using your brain.

If you would transfer your cargo by a ship, especially a few centuries ago, you would have to accept that some part of your ships will sink. And yet, you could make a profit, on average. Similarly, if you use human brain to plan your business, you have to accept that some part of your plans will fail. The profit can still be possible, on average.