For some time now, I've watched mineral deposits slow the flow of water
in selected pipes. Plain household vinegar does an excellent job of
dissolving it... if your can get the vinegar to the metal. Many years
ago I used it in my water take and all turned out well... though there
was no way of really measuring its effectiveness since the water wasn't
being restricted at that time.

Here's my thought; shoot holes in it for me:

By-pass the water tank, shut off the main valve, drain all pipes,
connect a small pump to the line between two separate faucets, pump
vinegar throughout the line, let set 24 hours, return all to original
and flush the system with water.

I've had this idea for nearly 25 years and did nothing. Now I see
there's a commercial service that brings their truck (presumably with
their pump and whatever solvent they use) and do essentially what I propose.

Q1) See any downside to the project?
Q2) See any reason why the outcome might be less than satisfactory?