Based on this article:
http://www.visguy.com/2017/11/19/detect-drawing-units-in-the-shapesheet/
My idea to help users use the right stencil on the right page (metric or inch-based scale) is to check both PageScale and DrawingScale for units used and warn the user he/she's using the wrong stencil for the specific page. (pages that use different units in PageScale and DrawingScale will always give a warning as this is a weird edge case, these diagrams are custom flowcharts not floor maps or something where scaling matters).
Is this an ok approach?
Will use stencil names with _M and _U suffixes of course but idea is to capture a user using the wrong stencil in case he/she's somehow is able to open the 'wrong' stencil for the wrong page (metric/inch-based mismatch). Or does this really not matter, in which case I'm worried for nothing.