Hmmm...
Well, Thaumcraft and addons are definitely a no-go, due to permissions, however I can set up configs for them so they won't conflict. Basically, ShneekeyCraft would ship with a bunch of configs for mods it doesn't have which are compatible with the mod pack, then you add those mods yourself and it bolts in seamlessly.
I do like Bibliocraft adding in some nice things to look at. Xeno's is kinda... meh. More magic than tech, really. Mystcraft would be a no-go for this mod pack. I'm surprised your friend with a potato for a computer can run with it, always seems to be a massive resource hog and FPS drain to me. But hey, I can always add configs.