Hi there,
My name is Andrej Szontagh I am full stack developer and designer.
I specialize in 3D graphics, rendering, shaders, path tracing, optimizations, vertex crunching, generative content, interaction and UX/UI design.
It's been quite some time I wrote anything in C++.
I mostly focus on Unity 3D projects.
From your description is literally impossible to make any reasonable judgment for the scale of the project. So my bid is for a month of work, but It could be easily a lot more. If we talk about MMORPG we don't usually talk about small code base.
I am OpenGL expert, don't have much experience with Direct X but it's just a more convenient API which does pretty much the same as OpenGL.
The only problem I see here is that to make multi-platform builds and testing I simply needs more platforms. I don't have MacOS, and also don't have Linux but technically that one could be solved.
However my field of expertise is rendering code so I can rewrite your code to be using multi-platform technology and you can work from there deploy yourself or find somebody else who will build for the platforms and do the fine tuning and testing.
If you would like to discuss the details please contact me on www.andrejszontagh.com.
(It's a temporary website)
On the website you can see even one MMORPG I was working on (solo) couple of years ago, did pretty much everything except asset modelling.
Best regards,
Andrej Szontagh