No reason to scar fresh land when we have plenty of land that is already well scarred, which could just have things like apartments over two stories tall legalized.

We already have cities, we are just refusing to build new housing in them.

And villages and towns that could become cities

One more comment on this, since I now heard the exact same point from a friend and talked more about this: we don't build cities. We build villages that grow into towns, that grow into cities. There are very few exceptions like Brazilia, which has lots of issues. Generally this to me is indicative that we are thinking wrong about cities. Cities aren't like massive buildings, but more like organisms. Three best results are achieved if we allow them to grow somewhat organically.

I recommend the book Order Without Design: How Markets Shape Cities or the short podcast of the same name.

Would these cities have the density of suburbs or be real cities?

The West Coast could use a new metropolis somewhere near SW Oregon, to fill in the gap between the Bay and Portland.

There's a reason one doesn't exist and that is because of terrain. It's thick mountain passes there from Redding to Eugene. It's much more geographically feasible to expand Sacramento or Eugene north.