There aren't really any "on skill use scripts", at least not in the sense that I think you mean. The skill functionality is implemented through their stats entry entirely, because that's where all the systems expect that information to be.
For instance, our AI doesn't parse scripts (with a few exceptions, like the FetchCharacterApplyStatusData you used and FetchItemSkillOnDamage), so it wouldn't know what the skill does.
That's not to say you can't do this - there is the OnSkillCast event in Behaviour script and the SkillCast, CharacterUsedSkill, CharacterUsedSkillAtPosition, CharacterUsedSkillOnTarget, CharacterUsedSkillOnZoneWithTarget and CharacterUsedSkillInTrigger events in Story to which you can react, but you're unlikely to find any examples of skill functionality implemented through script because that doesn't fit into the existing systems very well.
If there are things you can't do in stats or by extending generic systems (like your extension to the status interactions above), you may be better off going LaughingLeader's route.
In regards to trap skills: traps typically use normal projectile skills, exploded at the trap's own location with ExplodeAt from item scripts. If you look for "trap" in the Projectile stats table, you'll find a few examples of these.
For example, a mine works by using ExplodeAt(__Me,%MineProjectile,_TrapLevel,__Me), with %MineProjectile, by default, the TrapFireballMine skill. The other parameters are the location -in this case, the location of the mine itself-, the level of the explosion -a level 10 mine will do more damage than a level 2 mine but less than a level 15 mine-, and finally the 'cause' of the explosion, which, simplistically said, tells NPCs if a player caused the explosion.
