Took vinj's advice and had a look at sulit. There were quite a few late gen Previas on sale. It appears the space behind the 3rd row can handle 2 folded wheelchairs standing up with some room on the side for some more cargo. Of course it will depend on a final actual fit if my Mom wants to proceed with the purchase, but there's a chance.

What I like about the Previa is that it does not feel as big as the Alphard, and is not as imposing. Perfect, feels psychologically smaller, giving the prospective buyer more confidence that it's not much bigger than the Innova. Saves about 500-600k in the process. Though the 2.45m entry price isn't cheap