Darkness, that is a good idea.
Of course, the problem would be getting players to accept some limitations. On the other hand, I like to think there are some practical limits, other than cash, on what people can create for skill bonus items.
In some campaigns, somewhat more generous DMs might want to at least insure that the item creator possesses the skill. Of course, the question of Epic Skill Bonus Items or Epic Items in general comes into play. (I have never created a skill bonus item with more pluses in a skill than a character possesses. However, it seems that the ELH implies the existence of such items to reach some of the DCs of the more powerful Epic Level Spells.)
A very generous DM might allow Epic Level spellcasters more leeway in creating bonus items. Of course, any item with a plus greater than 30 should be incredibly expensive as I indicated in previous posts. Even if a spellcaster of 30th level is allowed to create a +60 Knowledge, Spellcraft item, he might be hesitant to do so at a cost of 990,000 market value or 3.6 million market value. (The cost of creating it would be half if you have the appropriate feats, but still half of any of these sums is a lot of gold.)