There is already Microsoft branded office software that meets each and every one of your critera.
Oddly enough, it's called "Office for Mac". There is absolutely no reason for Apple to take on Microsoft in this arena.
While I do like Microsoft Office for Mac, Apple can push the envelope by leveraging its high levels of innovation and the technologies already incorporated in its operating system.
Office for Mac has many shortcomings, and it really isn't a forward thinking software suite. There is plenty of space for innovation, but only a company like Apple would be able to challenge Microsoft's supremacy in the productivity software arena. Most of the advanced Office technologies are reserved for the Windows versions. These are the technologies used by big businesses in their workflow. Medium and small business don't, but they could. Apple could change this, and in time make inroads in big business.