Organization structure for Case study .... need yr advice

Question

Hi …I am in process of preparing an org structure for one of the company.
The company operations is like ….
The company has four factories in different locations and have 3 Regional distribution centers (RDC) across india. Each distribution center has 5 branches (Sales Offices), in this way they 15 Sales offices across India.
Most of the materials are procured by factories independently while some materials are centrally procured. Factories produce Finish goods and they are either sale to customer directly ( big regular customers) , or transferred to RDC to cater the requirements of other MID size customers and the other possibility to transfer it to Branches for Retail customers. RDCs also transfer FG to Branches.
All factories , RDC and branches have warehouse facility , however branches have limited warehouse facility as the customers supported by them are very few and generally deliveries are made directly from RDC / Factory.
They also have one R&D department in another location to develop new products and material is generally transferred from factories to R&D department.They also have one project division at the same (R&D) location which handles commissioning of new plants and procurement of capital goods.
Raw Material , Semi finish and FG are transferred between factories and FG material is also transferred between RDCs.
The group also has another Company which produces another line of products. RDCs and Branches of first company also work for second company (which means same RDC can store FG produced by both companies) and also Branches can also have FG material of both companies. Second company doesn’t have any specific R&D or capital division and R&D and capital of first company also work for second company.
Inter company transfer between both companies is a regular practice.
> Proposed Org structure
Company – Group Company
Company Code – First company and Second company
Factory Configurations
For first company
4 Factories will be 4 plants
Factories Structure (Storage locations / warehouses and storage type)
Since factories have different type of material ( like FG , Raw material , WIP ) therefore I am confused what option I should select 
1) 3 storage location ( for each plant) and one warehouse, 1 storage type
2) 1 storage  location and three warehouses (I think this is not possible in SAP , not sure ?? )
3) 1 storage location , 1 warehouse and 3 storage types
RDC structure
RDCs have full fledged warehouse facility and therefore thinking of making them also as Plant. Every RDC will have 6 Storage locations , 1 for First company RDC itself, 5 for associated branches and I feel each “RDC storage locations” should be a associated to a separate warehouse also.
( Since both companies produce different set of products therefore they will have different material and hence thinking of handling products of both companies in same plant and same storage location and warehouse , may be two storage type/area can be defined to differentiate material of both companies.)
Branches: Will be storage locations under RDC …..
While making branches as Storage location …. I have another question about valuation , since material from Plant and RDC is being transferred to Branches and  from there it is distributed to customers therefore the valuation of FG at BRANCH and RDC should be different as transportation cost , packing , unpacking etc cost should get added at Branch level.
Therefore in case I make branch as Storage location , I will miss the valuation part while if I make them as Plant then there will be lot of documents get generated for each movement. Hence not sure for what option I should go.
R&D:
Since R& D department is involved in testing in New Product development and generally material is required to be scrapped after testing therefore thinking of making it as Plant with one storage location and may be here I don’t need any warehouse (WM) here.
Project Division
Project division may also be a separate plant with one storage location and NO WAREHOUSE is required to linked with it.
Purchase Organizations
4 purchase organizations for each plant respectively and 1 centralized purchase Org for central procurement.
Your all valuable inputs are welcome .... looking foward to have a best possible configuration for above mentioned case study.
Regards

Answer 1

Phew... long long question
The rule I generally follow is that the org structure should map reality.
Company code - where Balance Sheet and Profit and Loss are prepared at the end of the year. If an entity does not do this, it is not a company code.
Plant
1) Each manufacturing facility is a plant (could be in 1 location or separate).
2) Each separate location is a plant (even if it only stores goods). May be an overkill, but helps when legal requirements change or the location is upgraded.
So in your case, RDC will be a plant (may be more than 1 if necessary). R&D should be a separate plant without warehouse management
Storage location
The only rule I follow is that there should not be any overlap of storage locations. So physically, any area of say 1 square foot should belong to one and only one storage location. Otherwise there is a lot of confusion during physical inventory. So logical locations are a no-no.
I usually use a lot of storage locations.
Don't have a warehouse spanning multiple plants (even though it is allowed).
Purchasing organizations
Have one for each location of purchase. If there is a team sitting in each plant procuring for only that plant, have it as a separate purchasing org (not strictly necessary, but makes authorization simple). For central purchasing, a central purchasing org should do nicely...
Hope this helps,
Lakshman