Now now, people, this could be pretty interesting...
There was a very promising Monkey Island mod for Half-Life called Plunder 3D
, but it seems to have died off. You *might* be able to get some people from that project interested in your idea.
If you get a team together and really start moving forward with this, I'd be glad to host your team's website on the Grim Fandango Network (I run it now). I'm sorry I can't provide any modeling, mapping, or coding support, but I can help you out in the web department if you need it
On a side note, ZeroXcape, the GFN founder, is a Half-Life nut, so he'd be thrilled to see a project like this put into motion. I like the game myself, but I prefer Quake III's engine these days.