Hello.
Sorry for the inconvenience, that was a bug caused by a typo. I have corrected it in revision a, which I just uploaded.
The first (crossed out) problem you encountered is actually a problem with RPGMaker.... sort of. In this update I added the plugin parameter to set the keybind of the switching weapons. When you updated your plugin, if you didn't go into the plugin settings to set this new parameter, it would be blank, as it didn't exist on your plugin settings. This would cause a crash the firs time the plugin tried to access that value, which is on boot. Removing the plugin and re-adding it fixed the issue because the plugin has a default value for that plugin command, but opening the plugin parameters and double clicking the new parameter, which would've been blank will also load the default value into it. Something to know for the future.
Edit:
I got a chance to test gamepads now that I'm at home, and the default 'shift' value for the keybind binds to the X button on an xbox controller, while control and alt don't have any equivalent on the controller. pageup is LB and pagedown is RB. I'm not sure how to set up control and alt as keybinds on the gamepad, but I think there are already plugins that do that kind of thing kicking around. So if you want it on the gamepad, shift, pageup and pagedown are all usable on the scene to switch weapons.