What is the legal ruling regarding the profits previously taken in exchange for mediation, and what should be done with the previous proceeds and invested capital? Is the proposed new method of dealing, which involves purchasing raw materials and adding an extra amount to them, Islamically permissible?

Your question addresses several matters. Firstly, the profit you take in exchange for investing the two women's money: if it is a fixed and lump-sum amount, it is usury (riba) and unlawful. If it is a percentage of the profits that increases and decreases, then there is no harm in it. It is necessary to distinguish between mediation, Mudarabah (profit-sharing partnership), and a loan. The capital that was paid is the right of the two women. The unlawful profits that have been consumed are excused due to ignorance, and whatever remains of them belongs to your friend. Secondly, there is no harm in offering to buy raw materials with the two women's money in exchange for profit, and you would be a Mudarib (investing partner) for the two women's money. Thirdly, increasing the price of a commodity for deferred payment. Fourthly, the legally permissible profit on goods.