Just to get this out of the way, this thread was not made to show what should have been in Brawl. I am in no way disappointed with Brawl, and I'm not so bored with it that I'm expecting another SSB game anytime soon if at all. This is just to share some of my ideas for a possible fourth SSB game.
I'll show you how this works. I'll post my ideas for things that could be featured in a hypothetical SSB4 given unlimited time, memory, and resources. And since I have so many ideas for it, I'll list them in a series of updates so as to save your time and prevent you from having to read a wall of text that you might rather skip over if you're not interested. Of course, being LuigiMan, there's no difinite time of day or week I can assure you that I'll update this thread, so just keep your eyes peeled.

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Stage: Balloon Fight
This stage is based on the NES game Balloon Fight. There are several hazards in this stage; a man-eating fish comes out of the water if you get too close. The clouds occasionally send bursts of electricity that cause major damage upon contact, though they don't have much knockback power.
One of the unique features of Balloon Fight is that you can't die by being sent to the side of the screen, because like in the original game, you will end up on the other side of the stage if you go to one side. This creates many interesting combo possibilities.
Character: Ridley
B - Flamethrower: Ridley releases continuous flames from his mouth, much like Bowser and Charizard.
B^ - Tail Spear: Ridley, his body tilted diagonally with his feet up, sticks his tail straight up (diagonally, actually) and rapidly spins his body around. Imagine Meta Knight's >B, but diagonal.
B> - Lunge: Ridley lunges to the side. If the attack connects, the enemy will be caught in his mouth for a few seconds, then spat out.
BV - Metroid: Ridley releases a baby Metroid from his wing and it goes after the nearest enemy. It causes minor damage and can be destroyed easily, and there can be no more than one released at a time.
Final Smash - After flying to the background, Ridley will release a huge white beam from his mouth. You can control the beam. Similar to Lucario's FS, but not vertical and harder to control.