I don't know if this counts as a sandbox 'option' per se, or just a general feature, but one thing that has been requested quite a lot is the traversible terrain heatmap for keepers. I think this is a really necessary inclusion at this point, especially as players get better with the terrain function and need to see specifically whether their keepers can reach certain points. For example, my current flamingo habitat seems to be a bit of a dud, because I put the shrimp feeding pool in the water, but the keepers never fill it. The water is extremely shallow (reaches the flamingos' knees) so in reality a keeper would be able to wade through it (and probably would), but it doesn't seem to work like that in-game. I'd also rather not ugly-up the habitat by adding some kind of wooden walkway, either.
It would be nice to know with a heatmap whether the keepers literally can't reach the feeders, or whether there's some other reason they aren't getting to them.