Hey its a pleasure, I'm glad you took the time to read my response - though honestly I never thought you would reply back so soon, hahaha!
It's great to hear what you have in store for this game - would definitely like to see more variations to the enemies in this game, too...
I think that Juggernaut monster is a really cool idea: funny enough, you mentioning creating a specific map for this creature made me think of a boss-type battle out in an open parking lot (think like at shopping centers) with the Juggernaut throwing Jeeps, Minivans, Half-trucks (maximum damage!!) and/or anything else it can find (including zombies?); however way you do it, though, I hope it to be fun and interesting!
Interesting idea of this blood witch - could it be the source of the entire infection...? Can't wait to battle this, especially as another boss-type.
I also would've loved to see a story in this game, but I'd also like to say, for me, it doesn't need to be a "complete" type of story - it would be nice if they're just mission-based - e.g. "reach room/safehouse X in Y time to rescue the civilians who got trapped because rescue teams got wiped out" or like where you reach a safehouse and then are told that you need to, maybe, clear one or two levels of zombies so they can safely escape the area or fetch some resources (food supplies, etc.) and get some rewards (interactions can be text based, I think like how Dead Trigger's "story" was, also its side missions).
Anyway all the best with your future projects - I hope you do well in the IMGA global awards, I bet it would help you get the exposure you need in both technical skills-wise as well as fanbase-wise!