Marvel can already use the Skrulls if they want, they just didn't in Avengers. Probably saving them for a bigger story, which is fine by me.
Personally I think a trade of Silver Surfer + Galactus for an extension on the DD property for FOX would be great. Daredevil doesn't fit too well into the current MCU anyways and FOX's idea for the reboot actually sounds neat. They have a point that if DD was put into the MCU it would probably be PG-13 and their R-rated-sounding idea seems more interesting for that property. Galactus and Silver Surfer would be huge gets for Marvel, especially if they are going to be delving more into Cosmic. They could be used in the GotG movie and/or future cosmic (and earth-bound) films. Doom would be nice as well but Surfer and Galactus alone are pretty huge.