Here's how I'd make the Generations Constructicons:
+ Release all the original 6 Constructicon characters (and try to use all of their original names, or approximate as close as I could if the trademark's lost (no more "Alpha Bravos" )
+ Engineer Hook to be able to form both Devastator's upper torso and right leg. Admittedly this would likely make Hook the most compromised of the Constructicons in terms of engineering, but considering that none of the other Constructicons need to be interchangeable, they should be pretty well designed and hopefully compensate for any of Hook's shortcomings.
+ Release a new Generations Prowl toy based on or inspired by one of his more recent IDW forms. Design this toy to be able to replace Hook as the upper torso/head of Devastator. I would only ever have this Prowl sold separately; if the Constructicons were to be sold as a gift set, I wouldn't include this Prowl. It'd make the overall set more expensive for an additional toy with a niche appeal. For people who really want a Prowlastator, they can go and get this Prowl toy separately.

As for repaint potential - I would seriously consider having this Prowl toy redecoed as Bluestreak and Smokescreen.