Item: Mushrooms

 We all know the two types mushrooms in Super Mario Bros. However, in the Galaxy series along with the New Super Mario Bros., there were many new types of mushrooms. I think we should see a few of these in the next Smash Bros. The mega mushroom could make you as big as possible for a little while, but is much rarer than other mushrooms. The bee mushroom could give you the ability to fly briefly without any limitations. Lastly, the stone mushroom could make you unable to be knocked back, but in exchange you'd be slightly slower.

Assit Trophy: Princess Rosalina

Another Mario character far from becoming a character. She'd be be another great option for an assist trophy. She could use a magic spell or something of that sort.

Mario Enemies

I think in the story mode, there should be some changes to the enemies. I primarily mean that enemies need to be enemies that actually appeared in video games before the Smash Bros. series. I'll start off with some of the Mario Bros. series enemies.

Dry Bones would be a great enemy that's gotten some recent popularity in Mario Party

Wigglers could be rarer, but more powerful enemies

A simple enemy that causes flame damage

Obviously, we need Thwomps to...well...thwomp some things

Dragons from Super Mario World would be a great addition

Beezos? YES!!!

How about some bloopers? If there's any stage with large amounts of water, these guys are a necessity

I wonder what these things could do. I think I saw them in a Mario game once

BLARGG!

A perfect choice for dark stages, easy enough concept too

Chuck Chargers are so annoying, but they still deserve an appearance

Do I need to say anything for him?

Dinorhinos. Just the name itself is awesome

Cobrats from Super Mario Bros. 2 would be an interesting addition I think

Flurries would just be flat out fun to smash to pieces

If these things didn't annoy the crap out of you, I don't know what will

Pokeys from Super Mario World and Super Mario Bros. 2 + 3 were sometimes difficult in later stages make them difficult to defeat in Smash Bros. too please!

Make Lakitu appear as a mini-boss!

 

With thousands of various enemies from the Mario Bros. series, it shouldn't be too hard for Sakurai to come up with a couple of real enemies, rather than those stupid things with beam swords who looked like mentally insane duck-human hybrids.