(and why do they have to strip almost ALL EXIF data, instead of just location? [yes, yes, fingerprinting, but there are LOTS of iPhone {NUMBER} whatever out there])
It really just needs to be clearly communicated, opt-in at attach time. Probably with a severely hidden, developer-screen level, or BIG WARNING in security settings to totally disable stripping.
I assume most people won't want it, _usually_, so when adding photos just have it be a double-opt in - you have to both hit an extra button during attachment, then select "include location" or "include location and metadata", then a modal warning/confirmation.
Something like: "Confirm including photo location? This will permit the recipient to see where the pictures were taken. <yes/no>"