Aren't Grob waiting for "a potential market" before proceeding with the 140TP development? I thought that a bit strange; I'm sure with the payload/performance capabilty (as you point out IO540) there would be plenty of roles, as well as those who merely want (and can afford) a four-seat turboprob aerobatic capable aircraft for private use.
(can't remember where I read that - a quick google search only reveals news from 2004).
I would also set up a new country with a CAA staffed by AOPA bods.....or maybe an aircraft carrier...!