As title says allow us to exchange all crops from farming into lower grade like onions,garlic etc. Atm cooking with materials from farming is extremly wastefull unless the recipe requires a higher number of the same ingredient. 

seeds too.   sucks trying to harvest your garden on an alt when you planted magical seeds and they can't gather it.

Save the leaves, when you want to swap gathering alts, turn in the leaves on that alt for Farming XP.  The Contribution points you get from farming leaves is worth more than the 2.5m per 20 leaves if you ever do any imperial cooking.