We just need one general idea for expertise feats.
With all weapon and implement attacks and with non-weapon non-implement attack powers that scale +2/4/6, you gain a +1/2/3 feat bonus to hit.
Every expertise feat can have the above text. Then add the special benefit, if you're using X, you can do Y.
If a barbarian with a +5 greataxe needs to throw his +3 javelin, is it really necessary to give him a -5 to attack because he doesn't have the proper expertise and proper enhancement bonus? If you're paying your taxes, your attack bonus should be fixed for real. And for the record, inherent enhancement bonuses really ought to be the default not the optional rule.