I think they'd have to get a pretty strong offer to trade Altherr, especially before he's shown he can do it in a real game again, the value of developing him, whether to keep or trade, is higher than it is now. If he falters you get nothing but how much would you really get now?
But Kendrick or no Kendrick, unless Altherr and all three AAA OFs (Williams, Quinn, Cozens) completely crater, one or more of them is going to be a bench player and one of them is likely to get traded. I'd still be surprised if all three starting OFs in 2018 are homegrown (could be Saunders, could be another free agent).
Klentak is not going to say to Mackanin "if you want Nava you have to be willing to cut Kendrick" because Klentak is the guy who traded for Kendrick. He can make that call if he wants to. He's not going to.
I understand the advantage of the four-man bench scenario, it lets you keep more of the players you want who are already on the 40 and Blanco and Coghlan can play all over the field. But what I don't understand is why that scenario would mean Hanigan or Holaday instead of Knapp, because Knapp can play 1B (albeit, he wouldn't really be available) and wouldn't require a roster move. A five-man bench of Knapp, Coghlan and Stassi requires two spots to open up but so would a four-man bench of veteran catcher/Coghlan.