This is a bit too specific workflow that you need to solve via scripting. Can you make it into a multiple master file so that the master 1 has the inline, and master 2 has the outline? Then run the following:
f = Glyphs.font
m0 = f.masters[0]
m1 = f.masters[1]
for g in f.glyphs:
for p in g.layers[m1.id].paths:
g.layers[m0.id].paths.append( p.copy() )