OK, I have a plugin design philosophical question for anyone interested:
I propose to make the following group options for shadow-casting:
1. Solids, Fall-through and Jump-through behavior objects.
2. Flashlight Shadow behaviour, to come with this plugin.
3. Object types that are added by events.
You can select any option and those object groups will cast shadows. However, options 1 and 2 will be supplemented by 3 - any added objects will also cast shadows. Also, objects can be added to an ignore list (for ignore object type rather than object instance) so that if you have a family of solids then you can select some to be ignored, for example.