Can't see how harmonization of rates makes the system more efficient as you still have 27 different VAT collection agencies 1 per country and most countries have multiple vat bands like this country anyway. Unless, the next 'efficiency' stage is for one tax collection agency in Brussels, so they collect it and hand it back to member states.
We all know what we happen then, Merkel and Sarkozy (or their successors) will sort that one out: 40% to Germany, 40% to France and 20% to the rest of the Eurozone to kick the Eurozone crisis can down the road a bit. Oh, and nothing left in the pot for the UK, I'm afraid. Still that's your punishment for vetoing the Tobin tax treaty for the City of London to bank roll the Euro rescue. Got'ya Ha, Ha!!!!

Tax competition is good as it helps keep tax rates down, different levels of state sales tax in the US seems to work okay.
The biggest barrier to a true single market in Europe is not having a common language like in the US. If you were going to pick a single European language it would make sense to pick the one most spoken as a primary and secondary language in Europe and we all know what that is don't we, yes Russian! English would be the obvious second language and France and the French could have a few concessions like Michelin starred restaurant menus, still written in French.

Keeping the VAT system as it currently is is vastly more efficient than collecting too much money from the poor and then having a vastly expanded bureaucratic system to give back again. Plus, there are many people that would rather be poor than end up in a world of benefit form filling and if they are self employed, spending half a day on the phone each time their circumstances change, so they and their families would lose out.
It seems to me the consultants who were paid to produce this report were given the efficiency framework by the EU and told to join up the dots.