Marc,
So you are stating that it would be beneficial to add more grounding to existing service entrance grounding ... by adding 1-2-3 grounding rods outside near the main electric service entrance?
Yes. It could, and probably would, be. The effectiveness of ground rods, as measured by the the wire-to-earth resistance, depends on several variables including electrical conductivity of earth materials, contact between rod and earth materials ("soil"), and geometry of rods and subsurface structures. So in general, more rods are better than fewer rods. If I ran the zoo, there would be a performance standard ( eg, require a measured, <5 ohm resistance) rather than a technology standard ( eg: 5/8" copper-clad rod driven 8 feet into the ground). But that's whole 'nother can of worms ;-)
(right now its the water main that is supplying the ground for the service entrance fuse panel)
Use of water line as earth ground was/is code-compliant . And at least in some jurisdictions, used to be required. A buried metal water line typically provides a low resistance path to earth ground. Which is Good.
However, in many cases, and apparently yours, the water line is located far from the entrance panel. So a transient ("surge") may/will take a shorter path to ground -- like through your electronic devices. Which is Bad.
The ground rod that is there today is probably not down much more than a couple of feet and only being utilized for telephone, cable TV, outside mounted antenna lightning arrestor. ground.
But the rod provides a more direct, shorter path for transients than the circuitous path through the water line, no? Are these two earth grounds are connected together at the entrance panel? If not, where are they interconnected? If it is through the very devices they are supposed to protect, the system could be worse than just ineffective.
Not sure of the methodology to bring this ground into the house from the service entrance. I've never taken apart the outside cover of the electric meter but do feel cold air coming in when I take the interior fuse panel cover off in the winter. You mention 6AWG bare copper wire for the ground.
First: Do no harm, including:
1) Do not even temporarily disconnect the earth ground with the main breaker closed (in other words, with power to the house), and
2) Don't break any seals on your meter box.
Do read read up on the topic. It may be that you can install the ground rods but have a licensed and knowledgeable electrician (one who actually knows and understands the issues of grounding to protect electronics!) review the installation and make the final connections to the meter and panel.
As with all matters dealing with AC power --as you will know without my pontificating -- safety and compliance with codes and regulations have absolute priority over cost savings.
Mis tres centimos ... Marc