I care less about the logistics of it (because let's face it, even when the show was at its best there were a lot of implausible things happening surrounding the movement and supplying of troops). The idea that the group wouldn't devolve into people looking out for their own family's interests when Sansa destroyed the unanimity is foolish (even the Dornish meekly go along/?.
The idea that the Starks wouldn't bend the knee to their own brother should have, despite Tyrion's speech, basically ended Bran as an option.