Layer transparency - Explorer for ArcGIS

[JamesBallard]

It would be great to have a transparency tool in the Explorer for ArcGIS mobile app. I generate .mmpk files with vector geology layers overlying geophysical imagery (as a .tpk base layer). It would be useful to make the geology layers transparent over the geophysical imagery instead of simply switching layers on and off (current functionality).  

Geology (vector layers):

 

Geophysical Imagery (.tpk)

Would be ideal to make transparent in the mobile app.