Not sure how easy it is, but I've found this which indicates it should be possible - http://borgsdemons.com/blog/2013/06/13/wix-and-nuget-creating-nuget-packages-to-deploy-wix-wixlibs-and-msbuild-tool-task-assemblies-to-wix-wixprojs/
Probably have separate packages for each .dll and a parent package that depends on all of them if you want the lot.
Not sure how easy it is, but I've found this which indicates it should be possible - http://borgsdemons.com/blog/2013/06/13/wix-and-nuget-creating-nuget-packages-to-deploy-wix-wixlibs-and-msbuild-tool-task-assemblies-to-wix-wixprojs/
Probably have separate packages for each .dll and a parent package that depends on all of them if you want the lot.