Hello Aman,
Please find the answers to your query,
1. Yes you can go for new requirement class with account assignment category as M which will ensure to have stock SO specific & will eliminate SO as settlement receiver. Your material will be then the settlement receiver. However I would advice you to go for whole structure of your planning strategy as replica of 20 without disturbing the standard settings.
Here are the steps to do the same,
a. T code- OVZG- Define new requirement class which is replica of 040 say Z40
b. Follow path IMG --> Controlling --> Product Cost Controlling --> Cost Object Controlling --> Product Cost by Sales Order --> Control of Sales-Order-Related Production/Product Cost by Sales Order --> Check Requirements Classes. Change the settings of newly defined requirement class here. Replace E with M. Mention valuation as M. Remove the settlement profile.
b. T code OVZH- Define requirement type which is replica of KE for an example ZE & assign the requirement class Z40 to it.
c. Follow path Production--> Production Planning--> Demand Management--> Planned Independent Requirements--> Planning Strategy--> Define Strategy. Here define the strategy for an ex. Z2 & assign the requirement type ZE to it. Same way define strategy group & assign this strategy to it.
2. Sales order costing is necessary for analysis of cost from SO perspective & it won't be compulsory. Still I would recommend to test the above solution in your test server & discuss the same with your FICO consultant before you derive any conclusion.
Hope this helps.
Mangesh S