Combining Galen and Protractor frameworks
Given the information available, I don't see a direct way to combine it.
However, Galen and Protractor are available on Github and I don't see any bigger obstacle from aligning/forking/modifying them to what you need.
The best shot I see is to contribute to Galen framework and extend their GalenPages.js with a mapping functionality to Protractor Page Objects. Though there are 600+ lines of code in that .js-file, it seems doable within reasonable efforts.
At least to open an issue in the Galen GitHub project in that direction would sure be worth the effort.