There are projects attempting to reverse engineer bistream formats. They are having some success but it is slow going. The last I looked some Lattice parts were

There are projects attempting to reverse engineer bistream formats. They are having some success but it is slow going. The last I looked some Lattice parts were mostly broken open. VHDL manipulation is quite advanced, see SpinalHDL. But they are limited to spitting out a blob of VHDL you can put into your toolchain for your device.