Id like to know if id be able to sell in game stuff for hard currency if i give people the option to pay for it with soft currency as well.like say for example i wanted to sell a rank that grants the ability to change the display name and their colour for messaging...would i be able to do that or should i scrap the idea.
If the item doesn't give gameplay advantages (like blocks or abilities like flight), you can sell for hard currency or soft currency. Anything that gives a gameplay advantage cannot be sold for hard currency, period.
So changing display name and message color is fine, as neither gives an advantage to the player.
If all the rank grants is a cosmetic ability, you're free and clear to do anything you wish. It's only when you add in functional features (ie, flight, easier ways to get better items, etc) that you cannot offer it as part of a rank package whether you pay with in-game currency or RL currency.