That was my thinking as well, although the idea wasn’t properly formed in my head yet so I held off posting until I could picture it better hahaha.
But yeah, I can see how that would be a cool and powerful method to spawn very complex landmarks – the idea of building randomly-generated dungeons gets me absolutely salivating!
Another thought, which I think I’ve mentioned in the past, would be to use summon stones for new landmarks as entities within the original landmark; using the same method that places trees and plants randomly. I don’t know if that’s the same loot-bag system you describe or a slightly different method, although the effect would be the same. The key difference is that in your method the entire landmark would spawn in a single large step, whereas my alternative idea would spawn the landmarks over stages (I think each summon stone would proc individually.) The benefit of that option is a possible CPU saving (less changes to compute at once/spread the load over smaller steps) and the potential to watch a landmark grow in front of you (e.g. grow an Yggdrasil branch-by-branch); although a big downside I can see is that one sub-landmark may block the spawn of another… although as far as I can tell there’s a chance that would happen even if all landmarks are spawned at the same time.
I agree it wouldn’t be a time save if you only wanted to make, say, a rock pile with a couple of different configurations to choose from; in that case it would definitely be easier to use aliases if possible. However, for really large/ambitious projects (e.g. the dungeon idea) this would probably allow a lot of shortcuts, e.g. by using randomised rotation and a couple of different loot tables (e.g. one table only for dead ends, and one table for rooms with connections to all sides, one specifically for hallways, etc.) you could easily enough build very different looking dungeons from only a handful of parts. That’s just using a pre-set floorplan with some of the rooms being randomly rotated while the hallways remain fixed – if it then got into crazy levels (rooms which spawn hallways which spawn another room from a loot table so you could potentially get more hallways off it, and so on…), then you end up with something that could almost be a game mode in its own right. Dungeons could become truly massive, adding a whole layer of gameplay from exploring that dungeon.