I planning on working with a project for infection. A Campaign Based Infection Series. L4D has always been used example but with that in mind people never looked around the map & just ran from checkpoint to checkpoint with no story. I want to add that story element without telling and actually show it in the game. The other project is sort of cops & robbers based map. This is quite a concept. Imagine you driving around in a warthog, while you get chased by the police (Infected) in Falcons & Warthogs. YOU decide where to go. There will be hidden jumps & other roads to jump from A-C with a matter of skill. Now how do you infect others? Well I think that should have to push them off the cliff. Assassinations are there just to make sure if they run willie nillie they can still kill them. Think of Need of Speed on Halo Style. Cops attack Robbers/Criminals by pushing them off the cliff & criminals try to get away with multiple roads & jumps. If you are interested in the concepts please contact Lil Devil9597 over XBL or PM me.
The first idea seems highly unfeasible. It would be almost impossible to tell a decent story through Forge mode while making that story playable. The reasoning behind that statement is the fact that many of the artistic forging styles needed to tell a story contrast directly with the forging styles required to make a functioning Infection map. If you really feel that you are up for the challenge, try to base the aesthetic side of your map off Hat's Checkpoint series. He really managed to immerse the player in a realistic world by blocking off LoS and funneling you into small but well-developed areas. If you can do the same thing there is no reason for your map to be unobtainable. As for the second idea, It's been done many times. Scrap it.
I've already done Hat's checkpoint series. The 2nd Idea actually hasn't been done on Forgehub. I can't really explain it so that may have confused you. I'll work on the project and try to show an example if I can.