"What about sticking the veggies in a foil pouch and shoving them into the oven?"
Well, I think this is a good idea, but it has its disadvantages. Some of the water may leave the veggies, stick to the foil, and completely evaporate, leaving a thin film of dry nutrient "paint" or "varnish" adhering to the foil.
Since this is usually done with aluminum foil, soaking the foil in water to reclaim the varnish is probably a really bad idea, as you will have aluminum compounds forming between the varnish and the nutrients, and aluminum is thought to cause alzheimers, and you will probably be able to taste it, as well. That said, if you avoid cutting the veggies into many small pieces, probably less water will leave them, than if you had steamed veggie pieces; more of the water, with its dissolved nutrients, will stay within the pieces of vegetable. However I don't like aluminum in contact with my food. While the risk of alzheimers is not proven, I think the chances are too high that aluminum in one's food is not a good idea, and that al coolware and foil, should generally be avoided.
Also, simply placing food on top of a layer of foil, would have less foil-to food contact, than completely wrapping it. Completely wrapping the food in foil would allow moisture to contact the foil, react with it, dissolve some of the aluminum into it, then drip back onto the food pieces. I don't think the amount is as much as cooking in an aluminum pot. Personally, I do this occasionally -- wrap a 1/2 squash or something in foil -- to bake it without charring it. But I feel a bit worried about getting aluminum into my body that way. I only do it occasionally. I could be wrong. But I feel safer steaming my vegetables in stainless steel cookware than oven-steaming it, wrapped in foil, even tho I do think there is less nutrient loss from the veg pieces, using the oven-foil method. I just use all the water that I've steamed things in. Consume it, one way or another. For example the other day I steamed brussels sprouts. Then I mixed some olive oil, garlic, salt, Tobasco sauce, into the few tablespoons of water that I had left after I was done steaming (if nece adjust the amt of water down by boiling it a few minutes longer), heated this just to boiling, then let it cool for a minute, and added a tiny amount of sesame tahini. I had a very nice sauce to pour over my brussel sprouts. I cut the sprouts in half and let them soak up the sauce.