There are some very known variants of figures out there that deserve to be in the line, like backpainted Tung Lashor, Redneck rattlor, Camouflage Kahn, etc.
The only question is: How should the be executed, so there could be a desire to buy them?! Bubble Power She-Ra has given a perfect example of how to make the perfect mix-and-match figure. You could buy two versions of the figure and then swap parts to create your favourite version of the character.
Here are my suggestions for quarterly bonus variants:
Battleground Clawful: Should come with Skeletor legs (like the 80ies variant), 200x inspired head and bigger shell armour on his back.
Camouflage Kobra Kahn: golden feet and Buzz-Off forearms, red painted mouth and slightly altered Clawful weapon. Could come with an alternate head for the Snakemen set (like one of the yellow heads in orange- think about it!)
Can you think of other mix-and-match variants?
Let me know! And please, don't tell us, you don't want variants in this thread, keep thinking positive!