Well, a lot of the concern I see people have is about each series having a specific tone in Smash with little variety despite having far more variety in their home games. This is why stage requests have a "Big 3" like character requests did at one point: Phendrana Drifts, Gangplank Galleon, and Bowser's Castle. For an example of tone variance outside of those, Underworld is a fairly important area to the Kid Icarus series due to being the starting area of the first game, but has no stage. Underworld is also an example of one of the few starting areas in a platformer/popular game on Nintendo systems that isn't just some boring old field of grass.
I would like to explain further, but my mind is naturally programmed to be laconic in order to promote laziness, so I'd have to get worked up about the topic in order to brainstorm a better explanation.
If you do start this, though, take care not to get booted off of your own project. Someone that posted a lot on the 4 Social had that happen. :/