The idea that a TARDIS would take six people to pilot properly goes all the way back to the original design for the 2005 series, in which the set designer surmised just that (or something for a minimum crew of three in usual situations, each managing two sides fo the pedestal). Why not have six consoles facing inwards, but to have six people each with a different function? If it were just one, I'd rather have one console (and a chair) to manage everything than be forced to run around a column all the time.
In the original series, we only ever saw TARDISes with one operator, namely for the Master, the Rani, and the Meddling Monk. All the other Time Lords seemed to dispense with a TARDIS entirely, timply popping in wherever and whenever they needed to do it. The most "modern" TARDIS we saw was arguably the Rani's, which had a round console; we could infer that as TARDIS design advanced from the days of the Doctor's type 40 (and whatever the Master and Monk were driving) that fewer crew were required for optimum operation, to the point that not many Time Lords even used TARDISes anymore when they bothered to leave Gallifrey.
This only leaves the "Rassilon Impermature", or the symbiotic link a Time Lord shares with his TARDIS. Under normal conditions, would a type 40 be linked with six Gallifreyans, or just the commander? It's impossible to know, but we do know that operating it with just one is okay.
Mark