You know the situation: you have set everything up for the client who wants to manage himself the content of his website. You teached him not to copy-paste directly from MS Word, and you told him to upload images at a reasonable size.
Of course, WP has been configured to resize all images appropriately, so there is nothing to worry ...
except that the customer will upload 10 MB images from his camera, at sizes of 5000 x 3000 px ... and WP won't produce any thumbnails for those, as the resizing exceeds the memory limit.
Question: can we define a maximum pixel width (of, say 2000px in any direction) beyond which the user will simply get a warning message?
Setting an upload limit in MB for any uploads would be no good though, since we should allow the upload of a 15 MB pdf, for instance.