I'm not certain McGee will become an average NBA starter. If you can get bigs like Kurt Thomas and Craig Smith for the minimum, is spending $10+ million a year worth the upgrade to McGee? I don't believe so. Not that I necessarly think Nic is a superior prospect, but I'd probably decline this deal if management projects it'll take $10million+ per year for a long term deal to resign McGee.
Interesting idea though.
The NBA is transforming to a league where to be a great team you need players that outperform their contracts. Lebron and Wade even on max deals outperform their contracts. LaMarcus outperforms his contract. Deron Williams outperforms his contract. Nic Batum on a $5.5 million deal will outperform his contract. McGee at $10+ million will not outperform his contract, and thus would not be a step towards making us a contending team.