Excellent ideas:
1. Automatic sell offers
2. change from 2 weeks to 4 weeks
Here's one more:
Change all offers over 100 into sell lots of 50 bushels. When a lord puts up a sell offer of 200 bushels, have the game automatically make that into 4 separate offers. That way, it's easy to buy a little and it's easy to sell a lot.
Without major changes to the interface, that would make accepting any offers (buy or sell) much more of a hassle. Instead of accepting one buy offer for 300 bushels, I'd have to accept
six separate offers for 50 each. And each of those offer acceptances would be a click on a "trade" button that would then reload the page. (It would also thereby increase the load on the server.)