I would love to have some sort of Miniature Painter/ Army Painter/ Item Painter.
Maybe I want my Iron-clad troops to be Painted in red for the 'Blood of the Emperor!'
equally, painting my leather-clad stealth troops in Mottled Green Camo and calling them "Commandos" or painting them in black and calling them "Ninja".
Firstly, the items and equipment to give them stealth-powers (perhaps reinforced by the leather armor and fur boots) is a cool game feature ... and secondly, the Painter (to paint said armor and items) would be awesome from an aesthetic appeal ... especially as it gives option to have units appear unique.
Now ... the practicality of dying leather a certain way, or painting iron armor (glaze? laquer? wax?) might seem either unfeasible, or perhaps require additional tech ... that kind of flexibility would be AWESOME!!!!
I mean, even in the main game, I could create units ALONG with their aesthetic paints and their custom Names, and have my Blood Angels and Emperor's Children.