So, the Item Familiar feat from Unearthed Arcana is incredibly powerful. It is the only feat I know of (hell, it's the only way I know of, including racial abilities, class features, spells, etc) to passively increase the numerical XP a player receives from battles and challenges. It also allows a player to increase his skill checks beyond any normal limits, while still using the skill points he spends on other skills. Not to mention he gets an Intelligent item that can cast spells or whatever as he grows higher in level.

I saw this feat being used during a single game. In that game, the player was playing a spellcaster (generic UA class) and the item in question was his +1 Longbow, that he later upgraded to a +3 splitting composite longbow, and he used a wish spell that he received from the Deck of Many Things (we found it at level 10) to add a special homebrewed ability to his bow that let it automatically adjust its Strength modifier to match his current Strength score (DM approved)

The character did not use the Item Familiar to add to his XP. Instead, he dumped all his extra skill points into Spellcraft, then took levels of Incantatrix and started Persisting everything. With double the normal ranks in Spellcraft, he was able to make those checks easily, so he had divine favor, righteous might, divine power, and bite of the werebear all Persisted, then he used the rest of his spell slots to do normal wizard crowd control while he rained arrows from above with his 42 Strength and his Wings of Flying magic item.

The DM was really concerned at this point, but she knew that if she just smashed the bow, not only would she be destroying an item that her player had spent all his money, crafting time, XP and wish to make, she would also be robbing him of about 40 skill points that he had put into the bow, which would not only remove his Spellcraft bonus, but also his ability to use Knowledge checks to identify all the crazy monsters we were running into, and et cetera.

It's an unwritten rule that nice DMs don't Sunder their players' gear. But the Item Familiar feat was written and "balanced" on the basis that if it got out of control, a DM could just take the item away.

This game has long since ended, I was just pointing out how the Item Familiar feat can be abused.

How would you all deal with an Item Familiar in the party? Please don't respond by "I would ban the feat", I know that's an option. I'm just wondering if there are any ways to allow its use without resorting to Sunder and still letting the rest of the party have a chance at not sucking in comparison?