How to batch update a combined network while preserving switch overrides?

[The_RF]

We're planning to move to a new RADIUS service for our corporate SSID. 

On the Meraki side, this only involves updating the Radius Server list / PSKs on that one SSID. 

My company wants to perform this update in batches, since we have over 1K locations. 

All locations are on the same combined configuration template. 

Originally, the plan was to clone the configuration template, update the Radius Servers on the new Template, then move networks to the new configuration template in batches. 

The problem is, moving a network to a different configuration template unbinds the switch profile, and removes all network-level overrides. That last part is a non-starter, since a good portion of our switches have at least one switch port override for one reason or another, and all of that would get removed. Also, there doesn't seem to be a way to audit overrides at an ORG level, even if we wanted to commit to re-configuring a huge number of overrides. 

So my only options seem to be:

A: Update the existing template, which would update the entire org at once. 
B: Split the combined networks into separate Switching and Wireless templates, cloning the Wireless template, then move networks to the new wireless template.

I'm hesitant about option B, not sure of the risks there.  
What's the best way to go about this, to update an ORG-wide SSID in batches, while preserving network-level overrides?

[alemabrahao]

I don't see why you can't do this in the template; worst case scenario, you can just roll back.

Just do it during a scheduled maintenance window so you can perform the activity without any problems.

[The_RF]

Hey, if I didn't have to answer to executives, I wouldn't even be asking this question. 
The stakeholders want a staged rollout.
To tell them we need to update the entire ORG at once, I need to list all the options, or demonstrate that I've sought other options and there aren't any. That's just how it is in my world. 

[alemabrahao]

So create a separate template and move the networks to this new template, it will be much less work. 😉

[The_RF]

That removes all network level overrides, as I stated in the original post. 
Also, it unbinds all switches from their switch profiles, which all must be rebound. 

If you know of a way around this, please share!

[nicdc01]

According to the docs; you should be able to unbind and retain the configuration including local network overrides.
https://documentation.meraki.com/General_Administration/Templates_and_Config_Sync/Managing_Multiple_...

This should be the case for combined templates as well as far as I can tell.

[The_RF]

I tested this for several locations. 

This only works as expected if you don't implement switch config templates. 

When you unbind a network from a configuration template (and retain configurations), configuration overrides are preserved at that point, yes. However, in the case of a combined network, any switches joined to that network are also unbound from the switch config templates they were assigned to. 

If any switches are then re-bound to a switch template, (even if it is identical to the original one it was attached to), configuration overrides are deleted at that point. 

So if you don't use switch config templates, this works.
If you do use switch templates, config overrides are removed once you bind switches to a switch template. 

The only way around this I can think of, is splitting the network into separate wireless and switch networks, updating the Wireless template, then combining the templates again into a combined network.