I love saag and I love the idea. Is $12-$14 per portion not too high of a price-point for SF? Given a 500 kcal portion, I would guess that is a higher per-cal cost than a takeaway saag dish in my area. I assume most San Franciscans and I are like-minded: if we can get the same thing delivered for less than your service, we will.
I have never seen seitan saag offered at any restaurants near me, but I love seitan. I even prefer seitan to meat, despite being a meat eater. I try to eat mostly plants, and I cannot digest lactose, so I usually order vegan chana saag.