Currently, in Glyphs, you get a warning whenever there is a problem with compatibility between masters (the red triangle in the font window or the red line in the glyph window). I wonder if it would be possible to change it (or to have the possibility to toggle it maybe) to whenever there is a problem of interpolation. This would allow to have different styles in the same file (roman & italic; serif & sans; sharp & rounded) without getting a massive unnecessary unreal warnings
Add “Enforce Compatibility Check” Custom Parameters, in your Font Info, and uncheck it