Not with mods, I built an insane hotel/casino with elevators and a ton of parts, wired up electricty, juke box and a lot of settlers and it ran great. MY biggest pet peave is 1 block per meter, which means you can't put a bunch of small decorations on top of a single block, and you are stuck on a 1 meter square grid, you can't build a house on a cul de sac. You can't rotate 360 degrees. We have some solutions there though for the next tech we've talked about. Hopefully we can overcome them for our future games.
I have also wondered about this aspect of the 7DTD voxel environment, why does every entity need to dominate and entire block, especially with little things that you mentioned, like putting small things on shelves and so on. I have also played with other building systems, more than just minecraft, which has a similar restriction. A lot of those are building within a pure static environment, so that's one thing, but very few that let you build that freely within a voxel world.
One I should mention, worth checking out even if only as a technical example, is Medieval Engineers, though I would call it far more of a Tech Demo than an actual game. There is no game, and it's weird, and mostly abandoned now, but that's Keen for you, similar problems with their other project, Space Engineers, both are super promising and hold tons of potential that is never reached. Their weird, you guys operate very differently, far more focused on game play experience.
Anyway what makes Medieval Engineers so interesting is it's voxel engine, and it has SI too, unlike many others. However it can be a pain in the #%! when your castle crumbles because a single foundation block cracks under the load, so the way in calculates SI is quite different than 7dtd. It also has wall, floor, etc system that is very similar to engines like Ark, not set in 3' cubes, but still obviously using a grid, but those chunks are more like 8' cubes. But what does make it sweet is how well it lets you place smaller blocks, and even disengage from any kind of hard set world grid. The walls and such snap together, if you want them to, but very little else does, and it allows for some really really neat construction. You can even work with beams and planks, etc. When you place base stations they do not snap to anything, one has to totally freeball their placement. And I love their shelves, they work like storage when opened, but the things you place in them actually appear on the shelf. They also have neat crates that display what is inside them on the outside, and how much of that item is in it too, only catch is it only works when is just one item type. But I do love standing back and seeing all of my inventory at one glance without any menus or additional signs needing attached and filled out manually.
My point is I think it can be done, not sure what the major differences are between the 7DTD engine and that one, but it is the only example I have found with that range of flexibility in a voxel engine. Also the world is an actual globe, it is super neat how that works, it has no edges, at all. You can move infinitely on a finite plain(sphere), basically. But it has no POIs to speak of, and very little, and quite abysmal, AI. It is just a sandbox, but as a voxel enthusiast I highly recommend at least playing with it to see what is possible in this type of engine. Plus I highly doubt they will ever finish it, someone needs to pick up that torch and bring that level of flexibility into a voxel engine, but within an actual kickass fun game, which is something TFP has certainly excels at.