If they want to axe the gil-farmers, strategically placing out of bounds killzones in areas they need to pass through for MSQ completion would likely work because they can't run their three DPS/one healer party set-ups if they're forced to remain in bounds and take hits from the later bosses and they're also too stupid to avoid the mechanics in solo MSQ duties.

For everything else, they should just be having a GM contact players who demonstrate suspect behavior like repetitive movement and/or abnormally long periods of activity time then banning them if they keep ignoring them.