Big Turbo kits cost a lot of money and people in the United States want to pay $10 for a big turbo/software. Companies don't like that. APR can do it cause they have enough staff and budget to specialize in both hardware and software (which is a good thing). Other companies (Revo/Uni) just do software and the most popular hardware stuff (exhausts/intakes) maybe because that's what's most profitable to them. BT R&D costs a lot more time and money.
I know AWE has the resources. They do turbo kits for the Porsche Turbo's (because Porsche customers will pay money for it) and they've offered semi-big turbo for the FSI stuff (GT28) if I recall correctly. Or maybe they feel like the market has been over-saturated with APR customers that won't sway over? Not sure.
GIAC probably knows about how AWE feels for bigger turbo's that's why they're providing support for CTS's GTX kit, the Frankenturbo FT23, GT3071 in Australia, and the Loba Motorsport ones (380/4XX). At this rate I don't know why AWE hasn't offered one given the time they've been in the market. They may change (and I hope they change) for the MK7 though :/