I'm assuming the thought process is that any trade bringing in a wing player like Redd would be sending Varejao out in the process.
I don't think you should assume that at all.
a) Ferry always wants a viable big back in exchange for sending one out, he won't assume a rookie (aka Speights) will contribute significantly until he actually does;
b) Anderson has a no-trade clause until December;
c) Milwaukee has no need for him;
d) If Ferry wants to dump Anderson because he's scared of dealing with Fegan again, you can bet most of the other GMs will be also.
e) We may have to trade Anderson AND the player we draft to get something significant back - unless we just take back a ton of bad contracts.
A lot of folks thought Damon would be shipped out of town a long time ago, but it's simplistic to just look at a player who's caused some sort of problem and then just assume he'll be on the next bus out of town. Sometimes those problems can be smoothed out ... and often the player simply has more value to us then he does to any other team. Afterall we finally were only able to move Hughes once we found another team with a player who had become equally overpaid and unmovable.
Heck, if Ferry is as worried as you of having such an old front court after moving Anderson, he can always just not move him. Seems the simplest solution.
But IMO age itself isn't a problem. What we need is talent, durability, athleticism, and experience. If we have to replace Andy, the best way to do that in the short term wouldn't be with a draft project. We'd likely do better via trade or with the MLE.