Love the new towers and the trading from SDBs. Thought possible new features that might be added in the future could include a message telling you when an item has sold out - similar to the message received when your meat collector is full - 'your (item) has sold out' and better still maybe a warning when it is at 10% or so - but maybe the message could go to local chat so you get to see clearly what it is that sold out. Another thing that may be very handy is an 'out of stock' ghost image of what you had in an SDB before it sold out - maybe it could even 'remember' the price you had set before it sold out.
I'm not a big trader myself but just thought these things could prove very helpful.