Out of curiosity, what are the features present in numpy 1.15.2 you want to leverage?
The reason packages that specifically include .pyd files (python .dll’s) downloaded with pip don’t work with Maya 2018 is because the .pyd’s were compiled with a different environment. Maya 2018 is built with Visual Studio 2015 64bit. Whereas the standard Python 2.7 distribution (and all packages containing .dll’s available through pip) are build with Visual Studio 2008 32 bit.
Because of this building numpy is not easy. Every version of numpy seems to have its own gotchas. There are a lot of dependencies you need to configure (ex: Intel’s MKL libraries). And you need to modify some of Python’s source packages, namely distutils, to get it to build with the right version of Visual Studio.
If you really really want to take a stab at it: This is the closest thing I could find to a guide.
If I have time by the end of the year I’ll take a stab at making a step by step walkthrough.