Well, I'm not a script expert by any stretch of the world, but might I offer a suggestion?
For the first boss fight, disabling items isn't possible w/o a script. However, having your items
confiscated by an enemy
underling is! Genius, no?

As for the second fight, you should assign all the skills (and/or weapons) a unique element for that fight, and make the boss immune to it. That won't stop people from using skills, but usually they'll stop after they see enough zeroes. Or if a storyline figure warns that the boss is immune to skills/magic, or has created an energy field that sucks all the power out of skills/magic, or whatever other minor plot idea. This way, you have more control over what's disabled than if you had a script.
Hopefully you'll get a script, but if you can't, then I hope that perhaps a suggestion will help you work around that.
Take care,
Arkaea