who doesn't love crossovers? and anyways I said that a knockoff would be fine. like masterdarwin said, it's basing the ideas on other games. even some of the most creative and talented game designers do this, so chill.
Cross-overs imply consent from both parties, this is just fandom. I have no issue with taking ideas, but when your taking the witch and just placing her in this game, it's not exactly taking an idea, it's taking the entire character. And I never pin-pointed which ones I didn't like, I think the Boulder character is fine, it fits well with the setting, and would be a good addition. But an energy sword? It doesn't work in this environment, it would just come across as someone being a fan of halo and wanting to throw it in a game, it's not professional (not trying to say you have to go all out pro, but seriously...). Also, "chill", lmao, I don't have much to say on that, I just find it funny that you had to include that in your reply.
I'll also throw this out there for the heck of it, I thought my idea was original. I don't know most of the zombies from L4D 2, so I didn't intend to use a similar zombie. Though, from the description, it actually sounds like a very different type of zombie, but if the "master" fellers think it's a clone, they can say whatever they want. I've been writing too many long comments lately.