Temporary WPF changes could be useful, but they would have to reduce your other WPF's at the same time. So set crossbow wpf to 100, but -100 on everything else. Would have to have some requirements that your build could technically have 100 wpf though (so you don't have 3 agi builds using them etc). Would be an OK gold sink too
Maybe its better to just let people reset their WPF with a consumable. Would be easier