I think that there should be a nether in Prison. It would bring more excitement to the game and give you something else to do. I think it would be a great add-on. -Just a suggestion.
If that was to be added it would probably cause more server lag, a long with the problem that end spawn claims will be valued less. And it would also be a big hassle to work on making bases in the nether too, and it would also give you a big boost to find soul sand there too, so people don't need to work hard to get it.
We will never introduce the nether to Prison or Factions. Minetime's policy for this is "Factions is about raiding, not about hiding."