Originally Posted by
Mr Kami
Well yes you can change what units to have this ability in unit_stats_land table it's called use grappling hooks.
But if you remove this it will completly brake gameplay during sieges since the AI has trouble enough with pathfinding as it is during siege battles.
The rate at wich they fall of the walls i have no idea what value might affect that to be hounest.
Anyway use packfile manager to open the packfile in question go to the table mentioned above scroll to the right and you will find this section with the grappling hooks change it from false to true or vice versa.