That's something I've been wondering too. I know that Mattel is pretty focused on the Classics line, but they've also been more willing to allow other products to be produced or at least planned such as the Bobble-heads and vinyl figures. And while there is some similarity in the design elements of these products, most people would agree that these products are far more cartoony than the motuc figure line.
So couldn't they produce new stactions as the opposite end of the spectrum? Instead of producing another cartoony product, the stactions would be more detailed in their design.
So perhaps they could offer the staction line as a subscription based series. Similar to what they're doing now with Castle Grayskull, they say if we meet this number of subscribers, then the line goes ahead, if not, it doesn't go ahead.
So I was thinking you could offer 6 stactions a year, in the form of two packs to save on production costs. For example...
1. Spikor and Battle Armor Sketetor
2. Moss Man and Extendar (with red Horde base, to swap with Leech, but also because of his origins)
3. Dragstor and Horde Trooper
For the most part I think the characters that make up these waves isn't what's important, the real question is how could we possibly see the stactions brought back?
But in saying that, I think there needs to be a character like Skeletor to get the attention of more casual fans. I remember Hordak got a bit of attention with the initial staction wave, and so I think Skeletor could act in the same way. You could always make him a convention exclusive to drum up interest and then include someone like Scare Glow with Spikor, but again, I digress.
The real question is, how do we bring back the stactions?
My answer, subscription based model.