so why not buy the cheap or decent regular usb hubs... they all require ac to dc adaptors... in which case you can use a regular 1-5A 5v voltage regulator... you can simply buy a 1A at radio shack for like 2 bucks... and other electronic places have them up and above 5A
so at the end you would have a 12v to 5v hub... and you can buy a few...
also can use a 12v regulator to stabilize voltage for say touchscreen
these voltage regulators can cost from $.89 to over 30+
i can see were noise could be an issue but thats a different story.
I also do not understand were you are getting that a device can pull 2A a USB one... i thought i read some place that the max is something of .5a hence why most 4 port hubs have a rating in put of 5v and 2A