Kusaris as a whole will see Junkers as foreign traders trying to dislodge their own companies and take their place--as well as opening the door to cardamine addiction of the youth and introduction of loose non-Kusari values.
It would be akin for a Kusari as it would be to you hearing that the Bloods or Crips were coming to open a crack lab, gun store and prostitution franchise chain in your hometown.
Elsewhere--Jinx has a good take on them.
Junkers are not a "distinct people"--they have a very distinct culture but are socially diverse.
You can take Outcast, Corsair and Liberty Rogue missions on Junker bases and also take Missions against Corsairs and others.
Several shippers (Aegeira and IC for example) have missions against them as criminals and Liberty rep goes up with authorities when you take missions against or kill Junkers.
Leave room to play "your Junker". They are diverse--one size does NOT fit all.
You can smuggle cardamine or "never touch the stuff". You can slave trade or find it abhorrent. Junkers mind their own business and strive to keep others out of it.
Play an individual--not a clone.
Their bottom line is profit and personal freedom unencumbered by someone else's values--plus absolute loyalty to their own and intolerance for incompetence or stupidity that puts them at risk.
That's some of my take on it but there is a lot of room to develop them. From simple thugs to mafia to clever and discrete geniuses.