I was wanting to repot them both in the same pot sould this be a good or bad idea
Traditionally the Japanese always use odd numbers of trees in a group planting. It seems to be more pleasing to the eye that way. But if you wish to use just two there is nothing stopping you.
I know you can sucesfully fuse different ficuses togther as long as their the same type but what if they arent the same type. would it work or would it just die.
Check out what Jerry has to say in the last sentence on this page.
He seems to imply that it is possible. But I agree that it might look odd if there are significant differences in the bark or foliage.
From your statement I infer that you have purchased two different varieties of ficus and are wondering how to handle them. In regard to your first question, different species are not usually mixed in a group planting either, but again the choice is yours.