Merging subsidiaries under a single MPN

Wandered if anyone had any experience (and found any pitfalls!) of merging subsidiaries with separate MPN's under a primary.

Obvious one is where the coop/rebate funding gets paid - can it remain at the subsidiary level or will it have to be paid at the top level?

Any other hints and tips?

I did find this https://learn.microsoft.com/en-us/partner-center/account-settings/merge-accounts