blind_s,
Good questions. I will give you my take for what it is worth. JBI seems to have the following hurdles:
1) Getting enough non-recyclable, clean, preprocessed plastic of the types the machines can accept. And in the process of getting enough of that plastic the cost is not so great as to make it not worthwhile. So your scenario in the right place would potentially help solve the problem of supply and cost of that supply.
2) The next problem is what if the sorters make a mistake and put too much PVC or other contaminants into the processor? Can the processor ensure a disaster does not occur? Sensors are one thing but a situation can go from fine to disaster in an instant and do they have the capabilities to forestall that event? And even if it does not cause a disaster, it seems it still could cause an interruption of production including full cleanout. Or a variation of this point, is if the machines had capabilities to handle more contaminants that could potentially provide a broader supply of plastic without production interruption. Currently it seems the machines are geared more toward the assumption of source separated, clean, preprocessed plastic. I am not saying this is unsolvable it just seems not addressed completely by JBI today.
3) Even assuming a nice supply of clean, sorted, preprocessed plastic, to-date the machines have not proven the ability to run above a fraction of their capacity. This is true even with HTF. That is why I spend so much time factually on this point with real numbers. The ability of processor #3 is a critical aspect of selling these machines at a price and terms that give the most benefit commercially.
To be clear, I do not think any of these are unsolvable just the current hurdles and your scenario does seem to mitigate some of the situation. Just my two cents.