I would like it if they did make a Wario World remaster, but as a nice plot twist, instead of the Giant Chest containing Black Diamond it contains another courtyard with another four worlds. Or, alternatively, they could go the Wario Land Shake It route and have extra levels for each world that you find through find secret exits (that is how you find the secret levels, right), or meeting certain requirements like Kirby's Epic Yarn, like, instead of the treasures unlocking WarioWare transfer pak dealies, in their place we would have the gateway to a whole new stage, that you'd access in the Big Chest area. Instead of those pedestals with the floating squares it'd be eight of those hatches that you ground-pound to access the red crystal challenges.
And then, as a Kirby's Dreamland 3 level plot twist, it turns out that beating those eight extra stages unlocks some sort of extra challenge that's like Pecan Sands on steroids, where it's the inside of the Pyramid or something.
Ooh! ooh! OR, even better, some kind of 3D reimagining of Wario Land 4 stages or something-- since Wario World in itself is already "Wario Land 4 but it's 3D" more or less-- and that could be your New Game Plus-esque reward for collecting everything. Keep in mind: it wouldn't be a cop out though, they'd still be legit Wario World level of quality, they'd just happen to share the aesthetic (but now presented in Wario World's gorgeous art style) and feature some of the original levels' gimmicks, albeit tweaked to work in the new 3D environment.
So, altogether there's Excitement Central, Spooktastic World, Thrillsville, Sparkle Land (had to look that one up), the eight Treasure Chest levels, and then the Emerald, Ruby, Topaz, and Sapphire Passages, with the Golden Pyramid being the final level or something.
If you feel like that seems a bit excessive, in that case I propose trashing Doodle Woods and replacing it with "Hall of Hieroglyphs but it's an actual level instead of a tutorial"