How it should of ended. (Spoilers)

The heist should have failed (like it did)

George escapes without being noticed and then they all sadly walk away.

Roger goes on holiday with his wife and has the realisation that she is his lonely maiden which would have been much more powerful having lost the painting

This would have also made the ending with the guard noticing it the Denmark gallery more meaningful.

It almost feels as this is where the directors head was at and then the odd scene of them on the roof was added later.