Indeed this is no longer possible because the coding works this way. Every item has a unique ID and when you change its color or position this is saved. So unfortunately dupliactes won't work because there's just this single ID they'd have to share.
In Flash it was only possible because I included the same item three times (= three IDs) for the "freestyle collection". So it wasn't even clever coding, it was just three items that looked the same and some boring extra work for me. 
The new "lock" system brings more possibilities because it works for all 1500 objects (soon 2000) and not just for 65 shirts. So I don't really think it's less fun this way, because instead of combining two bikini tops you can choose from a wider variety of tops. But who knows - perhaps it will be possible in the future to have duplicates? I would not completely deny it yet.
Regarding a "shapes" category: I remember discussing this sveral years ago and we came to the conclusion that it would be strange to have an abstract category only a small amount ot people asked for. And as far as I remember some of you told me the fun for them in building creative pictures was to use regular objects in a different way, so extra shapes would be boring. This is why I never included it. But there already are some shapes in the shirt motifes category and I see no reason why not to include more there. 
The button to turn off shadows should make a huge difference though, because I makesure more items than before will react to it. This will make it possible to use big items without shadows as shapes - not just hair.