I agree with your entire comment except for the first sentence. When working for a ideological goal, it is important to continually and earnestly evaluate what goals the imagined solution will actually fulfill, lest one end up misplacing faith in an implementation that can never achieve the desired ends.

First, this FPGA is still not implemented by things that are the lowest level - how do you know that 7404 doesn't actually contain secret logic looking for specific patterns on the 6 "independent" inputs (based on your widely-propagated design) that alter it's behavior?

Second, if one wanted to build an auditable CPU, they would not start by building auditable reconfigurable logic in order to develop a soft core CPU on top of it. This is a needless extra layer of interpretation, and the number one constraint you're trying to overcome is the constant factors that are left out of the Big-Oh notation.

We don't buy Intel processors because we're lazy and have money to burn, but because they contain a billion transistors switching a billion times a second. If you build something with 10k transistors switching at 10M Hz, something that would take 1 second on the modern CPU will take roughly 3 months.

So I think there's two properties to be achieved for actual Free Computing. The first is roughly getting something that can compute. These days, this can be done by buying a standard PC and installing your own software on it. This may not continue to be possible (so we would have to eg rely on integrating our own ARM chips, then FPGAs, then microcontrollers, etc), but trying to put a solution forward before it is necessary isn't going to get very far. There also is available computation that is unlikely to go away - Javascript in web browsers, available to all but sandboxed programming toy apps, etc.

Which brings us to the second quality of Free Computing, which is auditability - guaranteeing that the code running is doing what it says, rather than a subtle corruption which renders the whole sensitive algorithm broken. To get performance, we would like it if such a CPU could be made in a necessarily non-trusted fab, rather than independently assembled from discrete transistors. This seems like a harder, but yet better defined problem - meaning it might actually be possible to solve through some combination of clever proofs and bootstrapping trust up from an extremely simple auditable CPU.