Would a C++ CLI compiler be able to compile some large sets of C++ classes without modifications?
Is C++ CLI a superset of C++?
technically no, but depending how standard the C++ code is, you'll probably be just fine. when you get into windows stuff you may run into issues. I compiled the whole game engine we use at work in C++/CLI once and it worked just fine. A colleague did the same for all of mozilla and no such luck.