Half-life is by far my favorite game franchise, and I want to try to make an Eberron campaign that is inspired by the events in HL and HL2. Just looking for some feedback or additional ideas here.
I don't want to try to railroad the players through the exact plot of HL/HL2, but I definitely want the similarities to be striking.
Some bullet points:
-the Combine and other HL creatures originate from Xoriat
-house d'Cannith is analagous to Black Mesa
-the GMan is a dragon from Argonnessen in human form, trying to steer a prophecy
-the Mourning was created by an event analagous to the Resonance cascade, inadvertently caused by the players
-City 17 will be Sharn; Merrix d'Cannith will be Administrator Breen who is trying to realign the manifest zone from Syrania to Xoriat, sacrificing the city to do so (this could be the superportal/transmission plot line in HL Episode 1)
-there will be a chapter set in a town like Ravenholm
-most half-life creatures will appear as Xoriat aberrations
The end of HL2 Episode 2 is the closing of the superportal, trapping the combine. This might be a good place to end the campaign at level 20. That depends on what the plot of HL2:Ep3 is.
I think the biggest risk is trying to too closely follow the HL plotline, turning it into an obvious railroad. I am very aware of that, so that's one place I want to be especially careful.
I'm looking for helpful suggestions about how to do this well. If you don't get the idea, or think it's lame or stupid, please don't bother replying.
However, you have more game time than the computer game will allow, so you could set each location up with a series of smaller adventures. So the first adventures might revolve around getting out of City 17 (like the game) but at a much slower pace, and in a much more freeform manner. For example getting out of City 17 could be done in several ways - as Freeman did it in HL2, or through the acquisition of false travel permits so the players can board a train, bribing the right official or acquiring uniforms and pretending to be a combine patrol. You can give the players the options and they can decide which ones they want to do.
Maybe the players are trying to leave because their resistance cell has been compromised or betrayed - first they have to get to their former base (now crawling with headcrabs and headcrab zombies) and destroy evidence before a Combine forensic team can get there, once at the base they count the corpses and find out that not everyone was killed and then have to find the survivors and try and work out which of them is the traitor.
Then they have to eliminate the traitor/rescue survivors before they talk too much and then get out of City 17 before the Wanted posters go up, making escape impossible. By then the players should be 3rd level or thereabouts and you can plan the next series of adventures around the next location.
Players might get mini-quests such as seeding an area of City 17 with caches of arms and equipment for other members of the resistance to find later on. They'll be travelling through the city with piles of illegal stuff under their arms, trying to avoid patrols and get to locations on a map - some of which are very very dangerous.
The HL environment has a lot of potential for many different stories, and if you mix these in with the central plot of getting the players to destroy the Combine, then it will not look too much like railroading.