I can't tell whether there would be any sizable interest in that, but given the number of replies you got so far, I think you'll have to test that elsewhere if you really wanna know.
Be aware that there's already the UPDuino for that kind of form factor and the same FPGA (but the UPDuino has more IOs broken out.) I have a couple of these.
OTOH, the iCEBreaker-bitsy has a PSRAM chip (which the UPDuino does not), so that could be handy for some applications. Another plus is the DFU bootloader.
In terms of "software support", you can use Yosys and related open-source tools, but you can also use Lattice Radiant, just like with the UPduino or any other iCE40UP-based board. I don't think there's much of anything more than this to know, but maybe this particular project has already provided HDL modules for supporting PSRAM or various other things? Don't know.
So, personally no need for this, but possibly others could find it useful if they have never tried the iCE40UP, or any other small, low-power FPGA before. I think these are great for a lot of applications that don't require a beefy, expensive and power-hungry FPGA and for which people would otherwise resort to discrete logic, trying various contortions with MCUs to implement stuff they're not made for, etc.