Not sure how much you can say that lack of budget spawned creativity rather than it being more a passion project for Spielberg and Lucas which lead to the creativity of the production.
As for using alternatives to The Volume/stagecraft, not sure what alternatives could be used at its unique. I guess other green screen technology is cheaper, but its also not as technologically advanced and it can show on screen. So other than practical effects with on-site shoots, both of which are expensive and add to the budget, not sure what alternative you'd use.