Replace Steel pipes with Copper

thinkfuture

We are looking to purchase a 1969 House. The house has Galvanized Steel pipes for plumbing. This is bothering me & I would like to replace this with copper pipes.
Plan is to replace easily accessible horizontal pipes in basement with copper pipes & making a small hole in the bathrooms where is the main plumbing is connected & use Dielectric unions to connect vertical copper pipes.

Do you see any issues in this plan? Please critique.

joecaption

Not making since, if the old steel would be gone why the dielectric unions?
Hope your not thinking of leaving the main line galvinized, big mistake.
It would be far faster easer and less expencive to use Pex instead of copper.

thinkfuture

For internal piping behind the bathroom dry walls (I don't want to tear the walls right away) I want to leave it as it is & eventually replace it when I'm redoing the bathrooms. So the Dielectric union.
Copper is the code where we live.