Is it possible to use a local theme placed in the the same folder as your current beamer project? I.e. having a them in /project-name/theme/ that you can make updates to and get the changes instantly ...
I have a Beamer theme called beamerthemeMittweida.sty that's not available in a package. At home I just copied the .sty to Miktex\tex\latex\beamer, then updated all packages and I was able to use the ...