I've been giving some thought to Predaking. Obviously Hasbro won't produce molds they cannot reuse, but I realized not only can they retool the Predacons into a Maximal combiner, they also only need to make one voyager and three deluxe primary molds to pull it off.
First the Predacons:
Voyager - Razorclaw - Lion
Deluxe - Divebomb - Bird
Deluxe - Rampage - Tiger
Deluxe - Headstrong - Rhinoceros and Tantrum - Water Buffalo
Now the Maximals:
Voyager - Leo Prime - Lion
Deluxe - Airazor - Bird
Deluxe - Tigatron - Tiger and Cheetor - Cheetah
Deluxe - Rhinox - Rhinoceros
Maybe call the combined form Maximal Supreme?
Additional options:
Voyager - Lion - Leobreaker / Thundertron / Steeljaw
Deluxe - Bird / Bat - Sundor / Squaktawk / Wingthing / Ratbat
Deluxe - Panther / Tiger / Wolf - Ravage / Stripes / Snarl (Transformers Cybertron)
Deluxe - Rhinoceros - Ramhorn / Backstop
I'm sure there are even more characters to choose from. Also, I think it would be cool to have a combiner made up entirely of former cassette bots/cons. I only listed a few of them.
I expect nothing, and I don't know if anyone thought of this yet, so I figured I'd share and see if there would be any interest. The cool think is these are animals, not vehicles. I just wish I could figure out how to make the Technobots possible. Unfortunately I can only think to retool Nosecone into Energon Optimus Prime's drill limb. I suppose Afterburner could be retooled as Ransack. That's all I've got.