Would also love to see a nutricional comparison of each option. Some substitutions are purely functional, like the banana, but others are actually nutricionally superior like flax and chia seeds.
I feel like none of these actually work if you need an egg. Successfully made a tart for my vegan kid using a combination of stuff, including cornstarch and coconut milk using this recipe
And it was utterly successful. Not even oppressively coconut and not obvious cornstarch either. I love egg custard and this one was just as good, even to me. Eggs provide fat, protein, binding, rising. Nothing on that list does all of those. You really have to think through what you would be getting from an egg and build around that.