I made a comment in conversation on Twitter the other day that I like and need to think about more:
"A logically omniscient instance of homo economicus" is mostly just a good user persona to have in mind in your system design meetings
Despite being generally down on SEU, both as a normative and as a descriptive model, I think think this might actually be a good use case of it: Treat your system design as if it contains such people and ask what they will do will tell you useful things, as long as you don't pretend they are the only people using the system.
It's not dissimilar to the principle of design on the assumption that an abusive ex will be using the system: Abusive exes are not your main users (hopefully!) but knowing how they will abuse the system tells you important things about what you need to do.
One reason that this is an important user persona to consider is that people will tend to approximate it increasingly well as they get used to the system, and increasingly well as the amount of time and money they have available to bring to bear on it, so you can think of homo economicus as the user persona for people who are willing to sit down and figure out how to actively game your system.
A useful feature of both of these personas is that there's a continuum between normal users and them. Someone doesn't have to be an abusive ex to behave like an asshole to another user, and the tools for dealing with an abusive ex help there too. Similarly, if the system pushes homo economicus to awful destructive behaviour that you want to avoid, it will probably nudge normal users in that direction too.