I am thinking through this scenario: suppose an organization prefers to use a region-by-region migration to the UN to avoid a big bang migration, or the organization moves to the UN this year but next year they expand their service area significantly (or merge with another utility) and need to add the network of this region to their existing UN.
Would the currently available UN package tools support such scenarios? Could multiple asset package containing data from different non-overlapping regions (with identical data schema) be appended to the same UN?
What complicating factors or points of attention are there if the topology is enabled and the UN already published to Portal after the first asset package has been applied (and we have a productive environment), and only then the additional asset packages for the other regions can be applied?
Yes, that will work assuming there is no duplicate data. The asset package requires you to disable topology, which might be a good idea if you are loading a large amount of data anyways.
But the AssetPackage is probably a bit overkill for this workflow since you are really just loading data and not changing schema. I'd recommend just using the core Append/Import Associations/Import Subnetwork Controllers GP tools.