re: training in space
What about one orbit around the Sun: perihelion being Earth and aphelion being Mars?
That means a Mars flyby, of course, but at least, crews would get a taste of a long duration spaceflight in the solar system, without it being too long. I've read that such Hohmann orbit would only last one year.
Titov and Manarov spent one year in space, aboard Mir in 1988.