Hi Monica,
I would try to get an answer "why"? Why do you need this complexity of multiple sales orgs, sales offices, etc... in ERP? What do they do with this setup? Is their quoting/ordering process that complex or is the complexity the consequence of sales ops trying to organize their people to sell in different ways and the only way to model this in ERP is the complex org structure?
From a C4C/front office point of view you basically have two main functional considerations:
1. Access Control-> you need some way to restrict C4C data. This is best handled with Territory Management. You can define n-levels of Territory teams and an employee can be a member of more than 1 territory which allows extreme flexibility how you want to define how people work which will define how they access data using Territory management. This is meant as a LoB key user to define whatever structure they want to organize the people they see best fit to execute sales and be complex yet simply managed in Territory management.
This will restrict the user to accounts they can sell to or not, which starts the SD process. If you don't have access to an account you can sell to, there is nothing more. If you do have access to an account you can sell to, then next would be to apply any sales area specific conditions in SD, which is the second functional consideration...
2. Follow-up SD process-> you need some way to apply any specific price conditions in SD based on sales org, distribution channel, division etc...
This where you should replicate the above sales area data 1:1 into C4C account master and use this sales area data to drive the SD process of quoting and ordering and probably simplify the sales area setup in ECC (Does their quoting/ordering process need to be that complex?)
Assuming you have access to the account via territory management, why should you have multiple sales area information and result in different conditions? Shouldn't you have consistent conditions applied regardless of channel so that customers can't "game" the system to get preferential terms if they go through a specific channel or not?
Rei