I ain’t a C++ head, but if you have source, isn’t it nearly a nobrainer to compile to C#? I mean, yeah, pointers and garbage collection, but other than that?
The interface code could be converted to C#, the function code couldn’t, again performance and P code being too easy to disassemble and then a lot of bit fiddling in code which is more like C than C++ and the C functions probably aren’t there in C#.