I had this as a Bug, but with the recent update I am hoping I can get some more thumbs up from the users with this idea 
Right now the software continues to guess which unit of measurement my part was made in, and for me it has failed several times to guess which is the correct format, and blows my parts out of proportion in either direction (big/small). Built part in inches, units of measurement in the status bar are MM.
Your software could have a toggle upon file open such as:
Unit of measurement :
Always MM
Always INCH
Ask Upon File Open.
Have a box pop up on first run that requires a selection from the three.
Have the software open STL files in the unit of measurement chosen by the user, unless the user requires it to be chosen each time a file is going to be opened. That would satisfy all parties as most people usually use one or the other.
The box that opens upon “File:Open” would have MM or INCH.
Your “Settings” menu would contain a selection to invoke the original pop up box with the original three options.
Your original “Change Unit Of Measurement” selection would remain as usual.