OK, In that context, here's my "better idea"

The entire passenger module is attached to one of the gantries by a tether which is released just before launch.

In the event of a pre-launch incident, the doors of the shuttle are popped open and the entire module swings out and away from the danger zone.

You'd have to have something to catch it, and perhaps a secondary system to keep it swinging away and down to a landing spot in a large water-trough like one of those disneyland slides. That would quench any local fire and allow a little time for escape.

That way, you don't have to carry to orbit the escape equipment which you need only on the ground.

It would add some mass to make the module removable, rather than permanent, and strengthened enough to be swung. Depending on the way it's done, that might cost too much mass, but it's worth a look.