Unless you're OK with sim crossings becoming even more chaotic and crash-prone than they are now (points to the sailing and driving and flying aficionados who have been picketing LL for years now due to sim crossing woes) not doing even a preliminary preload of neighboring regions would be ... problematic.

See, your viewer has no idea of -when- you are going to attempt to cross from one sim to another, and shy of teleporting which puts in a load bar and can take all the time needed, if you move from one sim to the next, the idea is for that crossing to be as quick and seamless as possible. Therefore your viewer needs to have that sim's data in some form or another, and as long as it has it, it may as well show it, as this is supposed to be a contiguous world. As you mentioned, turning down draw distance should help a little bit. But it won't prevent loading of objects that you might get within draw distance at any given moment, so again, cached data.

One thing that might help is rendering off-region avatars as imposters. No animations, no shadows, no movement aside from very slow updates, they look like cardboard cutouts like you'd see in a record shop window. As you get onto the same sim, these imposters then resolve to actual avatars, but until you get there you don't need to know about all the fancy doodads they're using.

And yes, general best practices of Mainland building would be nice too. Things like actually using low-LOD models and textures for when an object isn't right next to you, low-rez textures for objects too small to see clearly even up close (you don't need 2K textures for an earring, or for tiled brick patterns) and sparing useage of 'animated' textures that cycle many different textures on the same object. I'm thinking cyclic neon signs, prop TV's, billboards, et cetera. As it stands now, anyone can do anything they want on a Mainland parcel as long as it doesn't violate the region's maturity rating. That needs to change, even if it's just social stigma amongst builders.

I understand your frustration and the intent of your suggestion. I know people who would enable your suggested setting immediately.

But I think there is a very big risk:

While mainland can be very chaotic on the one hand, on the other hand there are also many who recognize that they're in it together with their neighbours. We're not in a private sim where nobody else can see what we're doing. For example, if we thought about building a large skybox on the ground, many of us would think: wait a second, how would my neighbours feel about that? Maybe I should rather build it in the sky. It's the same outcome for me and doesn't negatively effect my neighbours.

If more and more people turned on this setting to not see their neighbours anymore, there is a risk that more and more people will build as if they were the only ones on the sim. And that in itself could end up making more and more people feel forced to turn that setting on.

If we think mainland is the wild west now, I see the risk that this setting could end up making mainland truly unusable for everyone who recognizes that mainland is a coherent world where streets and railways connect one place with the other.

If people don't want to see their neighbours, and maybe also don't want to be seen by their neigbhours, I think that is totally fair. Your only chance right now is to rent a private island, which is not feasable for most people. There is probably a product missing that gives people that option and is affordable at the same time.

Issue tracked. We have no estimate when it may be implemented. Please see future updates here.