Look, it doesnt make sense. It will cost too much more, have very little to mine and be at the whim of the antminer E3 pricing basically lol.
Most important question. WHY just WHY do u wanna make an FPGA when one asic already controls 64% of GPU mining? A few asics control most of the GPU mining already.
And this FPGA u are doing is just another GPU. Why? Because anyone can do it. U make a slightly stronger GPU known as FPGA. All u need is abit of dumb money going in there and u make no profits due to high difficulty.
In my opinion, interest to FPGA can be short-term, when you need to mine a certain number of coins before the release of ASIC. Like a Groestl, Nist5 and others.
But a more fundamental interest may be to offer a useful proof of work function which can also be ASIC-resistant.
By setting new standards for the usefulness of the POW function, we will strengthen mining on FPGA in the long term.
In the end, someone uses mega-FPGA cards in real life. For what? Amazon AWS earns with them, why not do the same?
Summary.
FPGA is not workable when one asic controls 64% of GPU mining market.
Lets say u use FPGAs and they now control 20% of remaining market via 8 algos.
One asic will appear and easily cut it to 15%. They will take the major coin away again...
Your FPGA is basically an antminer S7 and when new asic appears, it gets "downgraded" to be an S5. More FPGAs/GPUs will also join in the crowd as u earn less. U may not even be able to be profitable once it gets downgraded to S5.
Do note that difficulty increase does not lower profit, it lowers REVENUE. So, u may go negative on mining once it "downgrades to an S5". I strongly doubt it will work because the asics are far cheaper and too much more efficient and majority of the market is centered around a few big algos.
This is not yet including the biggest problem which the E3 that can mine eth, which controls 64% of the GPU. It can keep pushing more GPU mining power to the coins u are mining.
No point I keep repeating. I find it conceptually just a horrible idea.
Hope to see transparency in numbers and figures to brave souls those who attempt this project. Good luck people