This seems to me to be an unnecessarily complicated solution to a relatively minor problem, and would probably cost more to implement and manage than simply hiring another border agent (who can oversee multiple e-gates).

In my experience, the wait at the e-gates at T5 is usually no more than a few minutes. If there were an improvement I would make, it would be to implement a single queue for all gates rather than a separate queue at each gate, which frequently leads to frustration. (I suspect that this is the way that it's supposed to be, and that the staff simply don't know how to arrange the tensa barriers to cope with constantly-changing passenger numbers).