Add it manually?
I was thinking the same thing, but I might try adding it manually tonight. If this works then heck yes this is the best modpack out at the moment.
I really like DW20 and have been using his mod pack for my FTB LP series that I just started, but when I start my coop FTB series on my new channel I may use the Mindcrack pack instead if I can manually add the Mystcraft mod. That is if FTB Ultimate doesn't come out first.
Also to answer your first question this can be used as a SMP server. Just filter your launcher on "Server" instead of client. When you click the launch button you will then download the server files needed to run this mod pack as a SMP server. Then you can just click the launcher BAT file that comes with it and your up and running. I recommend editing the BAT file and adding a bit more RAM to its launch options. I've tested this modpack out myself and seen numerous videos of people playing Mindcrack on servers together. All the fun mods are there including portal gun and thaumcraft 3. Pretty awesome indeed!!!
Yep. We added it manually and upgraded the server to Mindcrack+Mystcraft. So far, so good. Everything seems to be working well. No ID conflicts in the world we have found yet, but you DO have to travel to undiscovered blocks to find the new blocks such as marble, etc.