A mixture of almond milk and silken tofu (1:1) will yield an inexpensive half and half replacement, top with earth balance margarine as necessary. For baking, flax or Chia eggs or commercial egg replacer should fit the bill. If the baking time is not too long you can incorporate tapioca flour in slurry for a creamier texture and extra thickening, our just use a corn starch slurry.
There is no way to know what they meant when they said "homogenized" - this really sounds like marketing-speak.
But if you are trying to whip shortening with water, you will need emulsifiers. I could imagine that the Spry already had them in. The "With cake improver" sentence in the can also points in this direction, as cake improver often contains lecithine.
You can try normal vegetable shortening. If it does not whip but stays separated from the water (it will probably break up into tiny droplets swimming on the surface under the mixer, but if you let it sit around for a few minutes, they will start coalescing into larger droplets, with the tendency to join into a single oily layer on top of the water), then throw it out and make a second batch, but add an emulsifier to the water first. Lecithine, xanthan, or guar will all work. Then you will get a really whipped shortening, something of a poor man's hollandaise. Work this with your flour.
You must be aware that while the crust made this way will be tender, it won't be flaky. A flaky crust is flaky because it is made from two different textures, the flour-fat mixture and the flour-water mixture, and they separate each other in sheets after kneading. If you mix the water and fat into a whip first, you will not get any flakes. You will get a shortbread crust, which is fine - it tends to be the standard pie crust in continental Europe. But if your goal is flaky, then you should follow the traditional cutting method, Kenji's easy flaky method, or the traditional boiling method.
Best Answer
I love capers and add them to different foods when I think it suits it. I'd much rather eat tartar (not tarter) sauce with capers than pickles in it. But them I'm not a fan of tartar sauce (maybe because of the pickles). If you add capers, rinse them first to remove excess salt, pat water off between a paper towel and chop finely. I think a tiny bit of finely grated raw garlic would suit it nicely. Let the flavours meld together in the fridge for a few hours too.