I think your looking at making a game engine. In essence your game executuable will be running the .pak file of yours and all you'd need to do then would be to make tools that create and modify new .pak files.

I'd reccomend looking into how games like Doom and Quake were designed. Also compression and file and memory stream functions would be of possitive use to you in this.

I hope that at least has given you some ideas where to look. Sorry I couldn't be more helpful at the moment.