Sarah could always guard the lander by sitting inside it... keeping it ready to go, and using it's onboard autocannon to take out anyone who bothers her.  She'd be a LOT harder to kill then if she was sitting outside it in a walker.  The Aquila Lander is MUCH tougher and has pretty much the same firepower.<br/><br/>It would save us room for an armsmen squad.  Unless Sarah wants to leave the lander behind and come with us, having her in a walker just to guard the lander is a waste.  The lander itself, with Sarah at the controls, is more than capable of defending itself.