Is Swift on the server a good idea? I don't own (or plan to own) a Mac. Does Apple support cross-platform tooling? I honestly don't know, but given their history, my default assumption is to be skeptical. Why would you choose this over Go or Rust? (Rust is totally sweet for server dev, and I've spun up a few Rust servers for things.)
For the unifying potential of the language: swift on the server (currently linux / freebsd limited), swift on mobile (Google seems to be moving in this direction too), swift on the desktop (macOS only).