Deathworld

Hi there Firstly, sorry for my bad english. I'm currently trying to editing Minecraft's Data Dir for being able to add 2 mod packs in one Minecraft folder. So there will be the .Minecraft, and in this folder there will be /ModPack1 and /ModPack2, both containing /resourcepack, /options... I think to just have to change mcDataDir, but I would like to do it with Forge, not with MCP. Is this possible ? Thanks in advance