How about

88 keys
Many elements of kronos soundengine incorporated in the engine of the pa4x/pa5x
Atleast 4 assignable knobs... including all kaoss parameters
Karma or another form of advanced arps
Integration with the ipad gadget app
Atleast 8 multipads
Daw integration
A usb audio interface..
So,ething akin to ketrons launchpads..