1. "Mixing of crops in a field" - from the biblical prohibition of using two different types of animals to plough (together) - also comes the prohibition of planting two different crops in the same field - or close to one another
Most hops are grown by themselves but some are grown with other crops at the base.2. Possible problems caused by Jewish farm workers working in the field on the Sabbath
That is possible.
3. The processing of the hop flowers into pellets; is 'something' mixed-in to make the pellet 'better' e.g. oils etc
I don't think anything is mixed in, especially not oils. The flowers are frozen and processed cold.4. Is the processing equipment used for other food-stuffs - and not properly cleaned between these different products.
I think only hops are processed by pellet machines. It seems you should stick to whole flower (or some people say "leaf" but it is the flower they mean).5. Contamination of the hops by bugs, insects etc. The FDA "allow" a certain (very small) % of contamination. Jewish dietary laws try and prevent ALL contamination.
Mites and aphids are common problems with hops. Pesticides are used to control this. Are pesticides contamination? Some specific varieties of hops are more resistant to bugs. I don't think the bugs end up in the finished dried hops though, so would that be okay?An example of this is Nori seaweed (and the consequences affect Irish Moss also). Naturally grown Nori attracts micro-size seahorses which become dried in with the actual seaweed. And so is not Kosher. Kosher seaweed is grown in ponds without the little seahorses riding around.
When hops are dried, they are kilned over a few days to a specific moisture content. I don't think anything is added.
Good luck and I think if you are serious and have money the farms will be willing to help you and could produce Kosher hops.