As we all know, the dilution of the Mythos deck is the biggest problem when playing with multiple expansions. I'm working on a software Mythos deck system that will hopefully solve this problem. Right now I have a program that allows you to choose which expansion to use. So you no longer need to remove/add cards and shuffle the big pile before playing. And you can set the environment and rumor cards fixed.
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Now that I have this, it should be easy to add new features. I'm thinking of expanding it so the user can chose the frequency of certain expansions (e.g. better chance of hitting a card from Dunwich or King in Yellow), remove the bursts, next act begins, double doom or double terror cards. Stuff like that. If someone has feature requests let me know.
Note: I'm currently not distributing the program. It contains the image of every Mythos card so there is a copyright issue. I've contacted fantasy flight to find out how they think about it. But I haven't heard from them yet.
I could distribute the program without the images, but you'd need to have your own mythos card images to work properly. You can download these from a popular source, but it takes some work.
I'll wait and see how FFG reacts before thinking about distributing it.