Do you agree with me that the factory should take care only of production and a separate company handle the marketing and sales?

It may be good for FMCG or other consumer items or commodity items. But not the different company, we can say seperate independent department of the company should do the Job. However for consistent sucess, a close contact/relation between Production and Marketing/Salesteams is a must, as Marketin & sales deptts can keep the production people abrest about changing or actually trending specs of the product in the market.

However for Speciality Chemicals, and especially products used as RM  for the end user for further processing, required a well nitted WEB of sales, Marketing and Production  team, always in close working relation. 

Yes of course , this the first the most important point in succeed in my personal opinion . 

regards.