Level Variations and Background Changer
Players should be able to choose the background they're about to play on. With different backgrounds come different level variations. Playing on a city background should result in destroyed cars with fire that effects players' health and helicopters flying over at random times with their spotlights. Shooting at some cars could result in their alarms going off, bringing you more zombies to fight than you would want to. And the windows part you were talking about. You know what I mean.
There are eventually going to be multiple campaigns that incorperate different themes anyway so... does that count?
Witches should pop up at random, if not the worst possible times. Imagine fighting a horde and some tanks. All of a sudden, a witch walks onto the scene. It will either just sit down and sob, or wander around. Getting close to the witch will result in you disturbing her and getting clawed to death. After killing her target, she will sprint across or around the screen covering her face until she runs out of the player(s') view(s). Anyone who gets in her way will get clawed slightly.
Showing up during a skirmish with tanks? That's... pretty sadistic...
She will probably be in eventually, but she hugs the top or bottom of the screen so she's actually avoidable.
Basically, players should not be able to choose their weapons. They will either start with a pistol(or pistols) or a melee weapon(will answer why next). The longer you survive, the more you help your teammates, and the more zombies you kill, the chance of weapons showing up increases. A 2 handed hand will show up and you and your teammates will have to decide who is in the most need of a powerup.
An important thing I've debated about weapons is whether to implement ammo or not...
If it winds up unimplemented, then the pistols can become a weapon soley to defend yourself on the ground and thus their is less clutter when weapon switching.
However, implementing ammo adds some more resource management to the game...
Anyways (back to your actual idea), like left 4 dead, you start with a random tier 1 weapon (shotgun or uzi, and I'm going to buff the uzi btw), but what I'm debating is the way you are given your extra pistol and tier 2 weapon. You're going to find them on the ground, but how often? I'm thinking that like left 4 dead, you should find them more sooner when you're doing terrible as opposed to doing well...
Stuff From L4D 2
Yes, in my opinion, I believe that there should be an ability to choose any of the 8 characters. The weapons should be part of the game, too. They will be purely cosmetic, however. The Charger would be an interesting infected to fight. The fire ammo should be a powerup, too. And....I'm not too sure about what I'm about to type, but if jets sometimes bombed where the players were, it would be cool. As more news is released about the game, some of that stuff could be added to the game.
L4D2 indeed looks pretty awesome, but there's probably going to be a lot of balance to be implemented in the final product, and I just don't feel comfortable adding the stuff until it's actually been released.
There should be a small timer on the screen to show how long you and your teamates have survived. Certain survival times result in medals and stuff and perhaps more than 1 powerup spawning at a time.
Medals... you mean achievements? Pretty early to be discussing that...
Your time could probably be displayed at the end of a level, and maybe a worst time could let the director give the player mercy.
But I don't know when and if that should come in to play...
Get rid of the fading. Just changing to the next screen would look better
You can actually click on the fading to skip it.