Many things are possible with what we have today on SRB2 v2.2.15, however, if it's a thing that applies for all the objects, it's quite hard to make it perform very well with SRB2 limitations, just as I did with Lighting System.
I think what I'll do is have a custom settings setting (via SOC) let you enable 1 of 4 settings for this idea:
OFF: If you want them completely off for some reason. Should be the default for addons that include the addon within it, with maybe a message at start to let them know it's available.
SOME: Specifically chosen objects that should have shadows (I make the list, but addon makers can add more to the whitelist). Like the player, large objects, and statues.
MOST: More objects have shadows. Only very common objects (like rings or common scenery, like flowers) won't have shadows.
ALL: Every object except specially defined ones will have shadows. The best ones to force them off are translucent, light/bright, and maybe older objects from srb2 (like a ring from srb2 the past)
And also render distance specifically for the shadows. Will use the same distances for the pre-existing distance settings.
So then those with weaker devices can still have them, just with less detail so it plays fine.
I'll definitely make a WIP post on the MB that will include my many other ideas (my brain comes up with so much, but i sort out unrealistic ones.)
EDIT: I forgot the final example on ALL.
