But you are right.
Replacing a offshore pump which doesn't need any energy source
by heat that doesn't move without motivation from a pump,
is a step backwards somehow

That's why I put this specific proposal in brackets and added a maybe

Add a 2nd floor level for pipes


What ?

Add a late game research xyz to enable
placing pipes at 2nd level above ground
plus making connections to floor level pipes (of course).

2nd floor pipes can cross ground floor pipes, if the is no vertical connection placed.
2nd floor pipes can run ...

Enable tree recovery from pollution

What ?

If trees are exposed to high levels of pollution, they loose leaves and/or becoming gray until (usually) they are dead.
So far (I think) trees cannot recover.

Proposal:
If damaged trees which are not dead yet
see zero (or very low) level of ...

overhaul the pump system

What ?

change name "offshore pump" to "water intake"
change function: it no longer pumps water, it only enables access to the water-ressource

to have water running in pipes, following needs to be attached to each other:
water intake <-> (optional pipes) <-> pump ...

Add late game upgrade path for rails and trains:
electric rails and electric trains

What ?

Add late game upgrade path for rails and trains: electric rails and electric trains
Research item xyz to enable the production of electric rails and electric trains
Research costs (high, including space ...