Very nice project.
There are healthy projects like OpenHPSDR that incorporate all of those things you don't like. Our radio does for VHF/UHF what OpenHPSDR does for HF.
We're trying to create the platform that can host a decade of software innovation. Thus, we do pay the cost of being on the leading edge. There will definitely be cheaper radios.
We're not selling kits. Either working PCBs, or complete radios. The hardware isn't under an Open Hardware license, although it's close.
The filter board slots are in the slides. Only one of the filter boards is shown. That one is meant to get spurious 60 dB down, but we've not tested it yet.
We have all of the right test equipment. Our main spectrum analyzers are Rohde and Schwarz FSIQ's, we have a high-end Agilent frequency generator, an HP Vector Network Analyzer with S-parameter test set, a GPS disciplined oscillator for the house frequency standard, a Faraday cage and an RF anechoic chamber, a lot of surface-mount assembly equipment, etc. I bought it all for cents on the dollar from companies like Nokia and Motorola that were shutting down R&D, the U.S. Government, etc.
By using gate-arrays, we get around some of the problems of unobtainable chips. We can move our design into different chips.
This particular design has an I/Q transceiver chip, and that's the only non-general-purpose chip. There are other IQ transceiver chips to which we could port our design.