Yes, the "workbench" would be indeed a great feat, some of my decks now have sideboards bigger than the decks themselves! 
Talking on the subject, it would be nice if in the menu for changing the card zone (deck - sideboard - bench) there was listed instead of "one - all", every possible option ("one - two - three - four - all"), so that when you have 4 copy in one zone and want to move 2 o 3 in the other, you can do it with one click only - just a minor nitpick, but it happens quite often when designing new decks.