Can modern all in one devices be used as a scanner with empty ink cartridges?

Most all in ones will ship with at least a partially full ink cartridge. Provided you never actually use the initial cartridge for printing, there should be no problem scanning. Never actually tried it, but I don't think that any manufacturer would require a non-empty cartridge (or even a cartridge to exist at all) to scan/fax.

I have the HP PhotoSmart C310, I just pulled all (5) the ink cartridges out of it and it still scanned a picture for me. It did throw all kinds of errors and complaints about the ink cartridges being damaged or missing.

Its actually the best flatbed scanner I have ever owned.