I plan on launching big, in all major languages, Mandarin, Spanish, English, Hindi, Arabic and Romanian, my native language. I'm seeking co-founders, natives in each language, with a common interest in psychology with good local links. I plan on keeping my technical cofounder close to me. Basically I'm building a new type of analytics platform ;)
You should share market, not equities every language that you have mentioned has a different market value, so you should research your potential market for every language and according to the outcomes of your research.
You should also be aware of the different banking systems and legislation of your partners. It is said that the recipe for failure is to try to make everybody happy, you will not make but can be fair. That means you have to show that you respect the efforts and the resources that everyone is giving and they are going to receive a fair remuneration for that. Remeber that they are co-funders and not your employees.
Multicultural negotiations use to be very complex and for big business that means in many cases, broken contracts and loss of opportunities, the good news is that they are not impossible, and with the correct advise you can go ahead.