I just completed the research for Coilguns and would like to upgrade my existing fleet for a damage boost. However, I'm not seeing an option for this anywhere. The only avenue I'm seeing is to design a new ship that uses Coilguns and build some of those. But if I have to keep incrementally upgrading tech and buying all new ships, then doing that again when I research the next level of tech, that seems horribly inefficient and I might want to simply wait for a few techs and batch them up in the new ship design.
However, if there is a way to partially upgrade already existing ships, that would be a huge benefit. I see an "Upgrade Fleet" option, but it is greyed out.