1) Create a backup of the default factory bank:
Go to .../VstPlugins/Gladiator2_data (PC) or /Library/Audio/Plug-Ins/VST/Gladiator2_data (Mac) and rename Factory.glb to Factory_backup.glb
2) Replace the Factory.glb with your custom one:
In Gladiator load your bank by clicking 'load all' and than 'save all' all Factory.glb
3) The next time you start Gladiator it will automatically load your custom bank.
Best Regards,
Markus