Functional Assemblies is a fancy name for "parts" — the parts of the system. Any design requires something like an inventory of parts and a review of how they function. So let's start doing a little thinking about that.
The basic elements of a hydroponics system are:
1) A nutrient reservoir or tank (I usually use plastic 30 gallon trash cans but anything watertight that doesn't leach anything into the nutrient would be fine), 2) some sort of delivery system to make the nutrient available to the plants, 3) plant growing sites, 4) support for the plants as required, and 5) a monitoring system for making sure the system works and continues working properly.
We've addressed the nutrient problem by buying a bunch of Total Gro 8-5-16. We've only thought a little about the delivery system. Right now I think a tank on the side deck with gravity feed to the passive plant sites will maintain the nutrient delivery. The tank will have a flexible hose with splitters to deliver individual feeds to different plant sites. To facilitate that design I've picked up a couple of Jim Fah's Smartvalves and for the sites that are not smart valved I'm planning to limit the nutrient with float valves. That only leaves the support system to worry about.
Tomatoes need a support system because they are heavy. Right now I'm thinking that using thin-wall conduit supports similar to those I've used on the NFT systems will fill the bill. We'll see when you go into more detailed design mode. I'm going to need at least twelve plants sites since I have six tomato varieties and I want to plant at least two of each. But if plans go as they usually do I may expand that. I don't want to have to pay too much attention to the system so that either will limit the number of plant sites or expand the size of the nutrient tank.