As you say, it's an experimental bed, so it'd be interesting to try something different, especially if you have the space and resources to do a "control" bed.

My main concern with your layers would be drainage. I'd do a small test plot and try a couple representative plants that you want to grow. Have you found something like what you are proposing in nature? And are you planning to grow something similar to what's found growing on such multilayered soil?

Here's my experience using lots of compost.

I have 5-6 compost bins and I've added lots of compost, and composted horse manure, to my community-garden beds over the years. When I've gotten sunken plots, the easiest way to fill them has been with compost and free coffee grounds, lightly forked into the soil. But I used to think I couldn't grow large tomatoes in my garden because of my cool-summer climate and part-shade garden plots. I added lots of compost, following the dictum "feed the soil, not the plants"! One fall I piled a bed with about a foot of partly composted horse manure, which shrunk to 6"-8" in the spring, and planted each tomato plant in 5 gallons of homemade compost. l had good production, but the big tomatoes didn't get as big as their genetics dictated, and I didn't get a lot of them. And then 3-4 years ago I started using a handful of alfalfa pellets in the hole when I planted tomatoes. Ever since, I've gotten good yields of large tomatoes, even in years that other local gardeners described as bad tomato years. I still haven't done a soil test, but the local soils tend to have enough potassium and phosphorus, and need only nitrogen, as far as NPK goes. I don't know the Ca-Mg ratio, and that would be a reason to get a soil test.

In fact, as I've come to understand, it takes only a small amount of added compost each year to stimulate the soil life. So adding the compost did not necessarily affect my yields, but it seems the compost was not providing enough N (assuming, of course, that the role of alfalfa was contributing N, but it also offers the growth stimulant triacontanol http://scholar.lib.vt.edu/ejournals/J...).

On the bright side, other people at the community garden have complained about the flavor of their tomatoes or sugar snap peas. When i've had the same varieties, we've done a taste comparison and mine were sweeter and more flavorful. I've also had fewer pest problems. I know a lot of other gardeners there use stronger ferts, such as chicken manure and commercial blends, and perhaps some of their problems are from overfertilizing. Pests are attracted to fast new growth, N ferts promote fast new growth. Watering is also a factor. Compost and mulch reduce the amount of watering needed, and withholding water from tomatoes, for one, concentrates the flavor.

I mulch my gardens, and I water by hand, so I can adjust my watering to avoid runoff. Mulch is a huge help -- it absorbs lots of water. It doesn't rain here in the summer, but during the rainy season, well-mulched (or planted) beds don't erode and well-mulched paths don't get muddy or waterlogged. On a slope, you can create swales (for absorbing water without runoff).