Will make some changes to master/worker mode asap, I too noticed it withdraws all, which isn't ideal for every situation.
As for selecting what to give to the master account, will try add a system in place, if anything I will just add a custom box so users can add items individually.
EDIT:
Will add a failsafe for trading when busy, thanks, really appreciate the detailed feedback usually I get vague responses, so this should be a quick update.