Lots of discussion about locks on here without a lot of consideration about what they do and how they're selected.
Most teams run with a tight head lock and a loose head lock. The THL is tasked with locking for the tight head and being an absolute scrummaging beast. He is also the lock who is required to do more of the grunt work, moving rucks ad tackling hard. They rarely have to jump, when they do its to create an element of surprise. Think Brad Thorn and Bakkies Botha as the two best recent versions. In Australia IMO the pecking order is Horwill, daylight, Douglas, Timani and Neville. I don't know which of those is the best choice now because Deans will only pick Timani who was clearly behind Douglas in Super Rugby.
The LHL is the line out jumper/caller and ball runner, who must also assist with the other tasks. He has to push in the scrum but is not as crucial as the THL. Think John Eales and Victor Matfield as good examples of the type. In Australia the pecking order is Sharpe, daylight, Simmons, Pyle, etc. Occasionally, two of one type are played, especially if you have a good LHL who is a good scrummager and works well in tight. You can only have one on the bench so that the replacement has to be good enough to fill in on both sides. But usually you should select one of each type for the run on side. When we had good teams that is what Australia used to do (think Eales and Giffen).
So if you want to drop Timani, don't put Simmons name up. One is a THL and one is a LHL. If Timani is to be dropped then the replacement is Douglas from the squad. He would substantially improve the scrummaging and now Kepu is out that will be crucial. Since Palmer was injured, we do not have a THP worth the name that we can select - the closest we have is Slipper and I guess he will have to do. I have high hopes for some up-and-comers like Ryan but not for Eden Park. The primary reason to bring in Douglas is to bolster the scrummaging at tight head. I would play Douglas with Timani on the bench, hoping that Sharpe stays healthy, so they can share the workload. Neither is fit enough to keep up the pace for 80 minutes.
PS. If Holmes/Cowan and Ryan haven't been called into the squad yet for cover then that is another reason on top of the hundred others why we need a new head coach.