The problem is that if we deploy 2 MB blocks right now we have to postpone SegWit. A combination of those would be similar to a increase to 4 MB which is definitely unsafe, especially considering that a transaction at 2 MB could be created that would take over 10 minutes to validate. It is either 2 MB block size or SegWit right now. Tell me again what benefits come with a 2 MB block size? None.