As @Kivax8 said, the problem with incorporating the EU into the new canon is the fact that it was often self-contradictory. Very few stories were collaborative, meaning that they often contained minor or major contradictions that resulted in them being placed on different levels of canonocity. With the new canon, you don't necessarily have to excise the EU, as the entire history of Star Wars is essentially a blank slate. A lot of EU concepts and characters have been hinted at, and even overtly included, most notably Grand Admiral Thrawn.
I don't think it will work well to have the original EU be an alternate dimension, because that detracts from the events in the core Galaxy. Alternate realities make for effective reboots, but Disney is nowhere near reboot mode with their Star Wars canon, so doing that now is probably not a great idea.