I think that would be a huge gamble and still leave the Spurs with a very, very sub par starting center.
Yes, every where else would be taken care of, but Timmy would still have the least amount of help out of anyone on the team and that is not good given his situation.
The young guns would have to perform at an extremely high level just to have a chance to help win a le and that is asking a lot when the FO is investing heavily money wise in Duncan's last years.
If the scenario you outlined comes to fruition, I would not be upset because overall the roster improved, but I think the Spurs would have to wait until next year to have a legit shot at winning #5.