Electrical – Alternatives to mounting tube sockets on a PCB

You won't experience problems with vias: 8 or 10 layer boards 1.6 mm thick are common, and then the individual layers are thinner than a 4 layer board of 1.0 mm thickness.
A 1.0 mm PCB will be less stiff than a 1.6 mm, but unless you want to place a heavy transformer on it (don't!) this won't be a problem either.
Standard thickness panels may be up to 635 mm (25 inch) wide, but your manufacturer will limit that for 1.0 mm thickness. Ask him how wide a panel may be.

Overall, a 1.0 mm board is a bit less stiff, but for boards up to Eurocard format (160 mm x 100 mm) I wouldn't worry about it.

These were common before the transistor and called "Phototubes". Every 16mm sound projector in the US schools had one to read the sound track on the film.

With higher voltage and multiple plates - one designed to emit electron when struck by light. The others are meant to kick out more electrons when they are hit by an energetic electron and you get a cascade. These are "Photomultipliers" and are still used extensively for photon counting and any very low light application like fluorescence spectroscopy or phosphorescence lifetime measurement.

There is a very fast and sensitive star tracking application that uses a spinning mask in the optical path to a photomultiplier. I have not seen one in decades even though they have a much faster response than CCD based tracking.

Hamamatsu is one maker of both devices in many forms.