Even if the referendum passes, I don't think the EU is globalists are going to abide by this let this stop them. Or at least the bankers. Also,

restricting the permanent resident population

There's your exploit. Just drop in a few hundred thousand "temporary" residents (well, whatever the maximum is anyways) while other countries continue struggling with hosting their own aliens. Then keep extending residencies as they lack adequate space elsewhere.

Even if the referendum passes, I don't think the EU is going to abide by this. Or at least the bankers. Also,

restricting the permanent resident population

There's your exploit. Just drop in a few hundred thousand "temporary" residents (well, whatever the maximum is anyways) while other countries continue struggling with hosting their own aliens. Then keep extending residencies as they lack adequate space elsewhere.