As i am thinking around the idea of using water as a energy-resource/storage.
It may be it could fit into your mod as very well, beside i feel you are much better at modding then i.

Generate a lake in your sense with dam-tiles (bricks, stones, concrete, steel)
It could be used then as storage area for the fluids you can place where ever on the map.

Secundly then it could be used as a pumpstorage plant if you could manage to use a normal pump using electricity to feed the water to the higher area and subsequently when in need with a turbine to get the energy back.

As a calculation i would say 10m high difference for calculating the energy turnaround looks resonably on Factorio
For more of 10m high-difference you could then cascade this construction.

Thanks for the idea nosports.

Dams are an interesting idea, actually. Though thinking about it, an entity which accepts water and generates power could be built, something like a hydro-electric generator.

Food for thought here nosports.

I vote for that!

If you ever get the "Dam" thing going, also consider introducing rain if it can be done, which occasionally fills up the fluid areas or Dam area.

this idea could already be built in very easily.

when offshore pump consume electricity.
and when offshore drains generate electricity.

so you can use water as an energy store.

only way this can be done is to have partial discovered lakes be infinite or it auto exposes a chunk back from the discovery line . if it still expands it's infinite if it's edge is within the auto exposed chunk from the discovery line. it becomes Finite. hence able to keep the fog of war active. how about when it reaches the 80% cliffs form around the edge of the lake showing the boundary of the soon to be emptied lake.

I was going to suggest that Dam-tiles be a thing but I see its kinda already been suggested :)

This seems quite cool :o (could use pipes to output 'used' water into another lake (one way ofc))