PowerShell is pretty common these days so I use it often as a quick way to invoke C# since that has functions for pretty much everything:
@echo off
set pathToResolve=%~dp0\..\SomeFile.txt
for /f "delims=" %%a in ('powershell -Command "[System.IO.Path]::GetFullPath( '%projectDirMc%' )"') do @set resolvedPath=%%a
echo Resolved path: %resolvedPath%
It's a bit slow, but the functionality gained is hard to beat unless without resorting to an actual scripting language.