Now let's say this happened in a shady way, and easily could without anyone knowing on a site like FFPC.
Let's say the league fills up and right before before anyone else looks, two owners email the FFPC and ask them to swap ownership of their teams. Let's say the FFPC actually does it. Let's say one of the teams paid the other team to do it.
I am not advocating for backroom shady behavior like this, but even if this did happen, nobody would notice, as nothing changes. Every franchise has the exact same assets. No trades were made.
Never mess with other people's money. Not even the appearance of it. That's a good solid basic rule of every day life.
If someone out there, right or wrong, fair or not, thinks you cheated them out of money, in any context ( i.e. you sold your entire team or sold a higher pick in a pick swap for real life cash), you don't know how people will react to that. If they believe that move eventually cost them a championship win and the money involved. Or some kind of consolation payout otherwise.
Some people, probably most, would sit there and take it.
Some people, however, might decide to find you, drive up to your place, and tune you up with a baseball bat. Or worse.
People say money brings out the worst in others. I don't believe that. I never believed that. I have always held money is the circumstance where the "mask" that most people wear comes off. And all you have left is the pure savage underneath.
I've seen people die over far less. I've seen people stabbed, shot, beaten, drowned, massacred over far less. What you are proposing is messing with other people's money. Or lending the perception as such. Nothing good is going to come of it.
Fantasy money leagues are are really a soft serve version of gambling. I'm not going to pretend otherwise. As soon as you mix what amounts to some form of gambling with money and questions about fairness in the process, things can go out of control very quickly. A couple of thousand of dollars might not be much to some people here, or could be a huge windfall to someone else, you just don't know people and their circumstances most of the time. There are people where the idea of you "gaming" them for a couple of hundred bucks or a thousand bucks is tantamount to asking for violent confrontation.