VoxEU has this piece by Daniel Gros and Stefano Micossi. Just one of many interesting points in the short text:
A potentially important improvement in the text agreed by the intergovernmental conference, and one that is often overlooked, is the fact that there will be two treaties: a Treaty on the EU, which contains most of the institutional provisions, and a second treaty ‘on the functioning of the Union’. The first is close in character to a ‘fundamental law’, or constitution at the national level, whereas the second is closer to implementing legislation. It is thus fitting that certain provisions (e.g. passage by qualified majority voting in new areas) of the second treaty can be modified by a simplified procedure. And herein lies the germ for an important innovation – a true two-level treaty structure with a fundamental law on which everyone must agree, and provisions on specific policies on which dissent is normal and can thus be modified more easily.