It is true that DnD 4th edition is probably the most balanced edition. However, according to my experience, it still suffers from min-maxing and feat taxing. While the result is not as broken as other editions it is still annoying for many players who wish to choose Linguist instead of another plus-something feat and be as capable as the rest of the team in stressful situations like combat encounters. So, the solution I suggest is easy to understand, easy to use and quite effective (though you may sacrifice some of the game's balance in order to do so).
So, here we go:

- Every bonus granted by a Feat is always considered a feat bonus. Feats cannot grant untyped bonuses or bonuses other than feat bonuses.
- Every bonus granted by a Power is always considered a power bonus. Powers cannot grant untyped bonuses or bonuses other than power bonuses.
- Every bonus granted by a Race is always considered a racial bonus. Races cannot grant untyped bonuses or bonuses other than racial bonuses.
- Every bonus granted by an Item is always considered an item bonus (Armor, Shield, Proficiency and Enhancement bonuses are excluded). Items cannot grant untyped bonuses or bonuses other than item bonuses (Armor, Shield, Proficiency and Enhancement bonuses are excluded).

In general, the above rules prevent the builds that are based to the abuse of the untyped bonuses. However, many feats may become weak or even completely useless if turned from untyped bonus to a feat bonus (the same may be true to powers as well as items), so you may need to either be careful not to choose something really weak (player advice) or do some reworking, especially to the feats, in order to reduce the unfairness (DM advice).