Yes, it is complicated. And yes, modders can do some placeables. That is true.
But what I’m proposing is much more robust and dynamically interactive for customizing a player-built base. Such a design can be used to create moats for defense (a water gap in the foundation tiles laid – not directly into the ground) as well as an aqueduct system (such as a suspended waterway – perhaps even with a waterfall end where channeled water falls and something like a waterwheel/buckets can take water back up). Granted, that would need some additional pieces not previously mentioned above.
The trick, however, is how to simulate both “dry” and “wet” versions of the foundation blocks so that they mesh well with existing foundation blocks. Being only able to type, I can really draw a picture. So let me try to describe the concept:
a. A corner “dry” piece (using a foundation block as a model) has two walled edges and two open edges and a bottom (a thin flooring about the width of a ceiling tile).
b. If four corners are connected together, you would have an enclosed space with an empty gap in the center. Only when the space is enclosed would it be able to retain water.
c. Players can now add water to the central space. If any of the corners becomes destroyed, the water (animation) drains/splashes and the three remaining tiles revert to their dry state.
d. Lengthening the ‘waterway’ would require side pieces. Two kinds of side pieces can be created: 1) one side with a walled edge and three open edges and a thin bottom, 2) two sides with a walled edge and two open edges and a thin bottom.
e. For more area, their may also be a piece for just a thin bottom and four open edges. Again, no water area can be filled unless the entire interior is sealed. Breaking the seal would result in the water draining and the “water” pieces reverting back to their “dry” state.
f. Creating a specially spillway “cap” would signal to the computerized mechanics that the open spillway (for a waterfall) would be “enclosed” but create the falling water animation.
If you wanted to get even more fancy, you can add triangular pieces as well.
The one problem I foresee, however, is making these building sets with blending the T1, T2, and T3 standard game pieces as well as each of the DLC pieces. That’s alot of artwork. If they just design the pieces and the art department can just slap an existing texture to them, that would be easy. But I suspect that because this are unique pieces with curves and lighting to consider, simply slapping a texture on them may not work right (and thus, require tweaking). If the devs decide to do this kind of project, they may decide that it uses only one standard type of building piece, like metal or obsidian or whatever, and not have to do other art styles or they may decide that this level of building is complicated and only accessible at the T3 level (thus, not having to do art styles for T1 or T2).
The idea would have to be further developed within the parameters of what is reasonably feasible within their time constraints.