Baking Static Batches at Editor Time

Hi there, I'm currently working in an open world game with static content being streamed in and out of the scene as needed.

In order to improve FPS we started meddling with the StaticBatchingUtility.Combine whenever a chunk is loaded into scene, but the method is unfortunately too slow and reduce our FPS to a drag.

to improve that I tried to use the StaticBatchingUtility at editor time to bake the meshes and objects, but the resulting meshes have many layers of protection against saving (hideflags, meshes not readable, etc...)

Another possibility I'm researching is improving the StaticBatchingUtility speed or at least reduce the overhead by spreading out the batching across frames, but even batching 2 objects resulted into large FPS drops, I even got the method decompiled, but given that it uses UnityEngine internal namespace I cannot tamper with it unless I'm using reflection (which I also couldn't get to work that well...)

tl;dr: is it possible to save meshes batched through StaticBatchingUtility.Combine / can I spread out the StaticBatchingUtility.Combine method through frames in order to reduce it's overhead?