I think the challenge for me is finding an action that has a locking bolt handle, sub 90° bolt throw (60° or thereabouts) and is extremely smooth regardless of any lateral loading on the bolt (big problem for most actions). Run the bolt on an Accuracy International which also has assisted opening in the form of a plunger in the cocking piece housing and try to make it bind and you'll see what I'm talking about.
I've been working on a custom Kimber 84M and it's almost as good as I can get it in terms of the features and performance that are important to me but it has a 90° bolt lift, and the action is no where near smooth enough, even without lateral loading. I can live with the bolt rotation issue since I added an adjustable comb so scope clearance isn't a concern, but the smoothness of the action is not an easy fix. Salt nitride of the receiver and bolt might help and that's in the plan.
The Kimber 8400 actions which I much prefer, always have and always will be much smoother than the 84s due to the larger bolt bearing surface and consequent support of the bolt. I'm currently building a custom 8400 6.5 PRC but due to the lack of availability of an AG Composites lightweight stock capable of being inletted for bottom metal I won't be able to build the equivalent version of the 84M. And so it goes.