Except the TOS Enterprise is described on screen as having impulse engines, right?
How is that relevant? This thread is about reinventing it from scratch, pretending that TOS never existed.
Is it? Vektor's idea, which was well-received was that we might consider TOS to be a radio-play and that we would design the ship only from the dialogue.
If, however, you wish to pretend that TOS never existed, then it clearly does not matter how you design the ship at all. If so, it's not really a redesign Star Trek challenge but, design a random space ship challenge.