A "patch" addon which happens to override or edit a class from another mod will become a dependency in a scenario. When this occurs and the patch addon is subsequently removed, even if it added no units to the game and does not appear in the mission, it will forbid loading of the map: clicking "Close" will simply load the empty map. It requires manual editing of the mission.sqm to cull the invalid addon, and if the scenario was binarised (which the game now does by default) the map must be run through additional tools to unbinarise to be successfully recovered, which is an extensive process.
I propose that we be given a checkbox that, when checked, allows us to load the mission anyway, with a warning that the map may not behave as originally designed.
Specifically:
1) If a mission is missing addons, in the dialogue box that appears, include a checkbox: "[ ] Load without missing addons". Other possible names are "[ ] Load anyway" or "[ ] Ignore mission addons".
2) A tooltip should appear over the checkbox: "WARNING: Scenario may not behave as originally intended due to missing addons!"
3) Any invalid class should be removed from the mission upon loading if this checkbox is marked, while still allowing all other valid classes to load as normal.