I encountered this just the other day while fixing up stats for a TARDIS I'm using in my game. I fully understand modifiers due to the Tech Level difference, but I'm a little stuck on two things, as mentioned above.
For Tricky Controls (6 pilots) for the Restriction, how does this work for a TARDIS with less than six pilots? Currently I'm running as a cumulative -2 penalty for every person not at the console in conjunction with the TL differences. But is that how the Restriction works? I'm not sure I'm seeing in rule mechanics how the Doctor overcomes this.
As for the Vortex trait, are time machines just unable to be used without it, or is there just a massive penalty involved? If so, what is it? Any clarifications here would be greatly welcome.
There was a thread in the Rules Discussion section a while back that touched on this. I don't think there was a general consensus of opinion, but one suggestion was that there should be a bonus for each additional operator after the first, rather than a penalty for fewer than 6 operators.