Or how about a Dr Who Dalek collection? All the different types/colours would make for a reasonable length of partwork, make each one large enough and it could be multiple issues per Dalek.
From 1963 onwards there have been a number of different colour combinations of what is probably the most recognisable 'baddie' in the Whoniverse and beyond. Just off the top of my head you can get:
TV version "Dalek Invasion of Earth" Suprememe Dalek (Black)
Film version of the above
TV "Planet of the Daleks" Supreme Dalek (Black)
There are at least 6 versions of Black Dalek when you include "Rememberance of the Daleks", both movies, and the earliest stories.
Then you can add in the white ones from "Remembrance", the metallic ones most often seen, the rare red ones and gold ones. The there are even the bronze ones from the modern series, the green British WW2 Dalek featured in one story, and if you get desperate enough, the 'palitoy' Daleks known as the "New Paradigm".
And don't forget the specials, several daleks were equipped with non-standard weapons, such as cutting torches (various stories, most notably the movie version of "Dr Who and the Daleks"), projectile weapons (Death to the Daleks) and the very "Special Weapons Dalek" from Remembrance of the Daleks"
Maybe even throw in a chance for subscribers to get the variants of Davros too, Genesis of the Daleks, Resurrection of the Daleks, and Remembrance of the Daleks spring to mind as three different variants.
EDIT: Or how about a Dalek, probably 1/4 scale, along the same lines as the current R2-D2. That's a project I would get in a second! Autonomous Dalek, possibly LED or low power laser pointer weapon, lights flash on speech, multiple phrases built in, eye stalk turns towards sound, maybe even offer a choice of classic or new bodyshell. (If you can't offer the choice, go for the classic, it's recognised by more people and gives more options for paint so that people can make their own version.)
You could also sell 'customising' packs with things like movie bumpers, power receiving dish, etc.
Current Builds
Eaglemoss: Ecto-1, BTTF Delorean [Installing Mods]
Hachette: T800 Endoskeleton
Agora Models Shelby Cobra 427 [Plate 031]
BanDai 1:5000 Imperial Star Destroyer
AMT 1991 U.S.S. Enterprise Bridge [Installing Mods & Lights]
Finished Builds
Deagostini: R2-D2 [Never getting batteries]