jhallows,
First, what you are missing is the core logic bridge. In a system, there are two types of chips that connect the processor to the standard PC peripheral set. They used to be referred to as the core logic chips and the I/O peripheral chips. Todays terminology is the North and South Bridges (and use PCI for connection between north and south bridges).
The core logic converts the processor bus to a set of high speed peripherals that the processor needs to run. Typically this is the SDRAM controller (for 486, it probably will be EDO or FP DRAM) and an ISA bus. The ISA bus is then connected to the 82c206. If you are not familiar with the ISA bus, then see the PC104 page.
Since I saw that you did not want to really use any external chips (north bridge or core logic) then your only option is to roll your own core logic. This is considered to be medium to very complex depending upon the amount of functionallity that you want to add. Remember, you need RAM, boot ROM, and some sort of ISA bridge as a minimum. Many vendors choose to implement more. If you really want to roll your own, I will try to pull out some of my old stuff to help you out.
If you do want to use a core logic chip, let me know. I will try to find a vendor or two that still makes them (this will be tough). Candidates were (and still might be) ALI (acer labs), Chips and Tech (now intel), OPTI (not sure if they are still in business), and maybe SMOS (seem to remember they were thinking about it. Another vendor that I did a design with was PicoPower. They were acquired by Cirrus logic and then they sold off to national semi. I don't think they sell the product anymore, but it was the PINE chipset. This and the 82C206 pretty much took care of a lot of stuff.
Just a suggestion or two, If you are trying to learn about 486 design, the you are heading down the right path. If you are trying to get a 486 system built, check out the Intel 486GX hummingbird chip or the AMD SC400 and SC500 elan families. They provide a lot of what you want already packaged up.
robotman