No, right now it's not possible, the "global default" is current hardcoded in the program. We might try to add some kind of customization for it in an upgrade.
The Pushback tug is placed at an angle because when you are taxiing in, there might be a marshaller and, since the marshaller position can change over the longitudinal axis depending on the parking size and your eyepoint in the cockpit, there's no safe place along that axis to be sure they wont clash with each other so, the angled start is the safest position.
