I would avoid the two language problem so option B is out of the way. If you choose option A, then you run into a risk of having to optimize some part of the code in C/C++. So you end up with the two language problem again. If you care about performance, then option C is not a bad place to be. Learning Julia is not a big deal. It would not take a seasoned developer too much time to get up to speed with it. What I found is that the Julia community is so vibrant that you can get a lot of help to move along quickly. My two cents.