Very interesting topic! I´ve said this before, but this is actually what got me into Rebels, since I´m a big fan of the Jedi Knight series and Jerec is indeed a favorite character of mine. Personally, I´m still trying to work out the fact that the writers are assuming the Inquisitorius is over by the time of ANH. It´s hard to make sense from it because the ending of the Jedi Order doesn´t automatically means there will be no new Force users in the whole galaxy, and that no surviving Jedi will have any interest of working against the Empire. On the contrary, the Inquisitors are great assets, like the Sixth Brother proved on the Ahsoka novel when he single handedly ended a problematic rebel cell. The thing is, canon Inquisitors are now very combat oriented hunters. Every single one of them is extremely arrogant and sure of themselves, to the point they even overestimate their chances in some very difficult situations (Malachor), and preferred death to face the punishment for failure. To me, that indicates that they have very high success ratio; we just haven´t seen this on Rebels. The Inquisitors of old, on the other hand, were mostly interrogators than could have talent with the Force, and even lightsaber skills (Jerec was prominent in both, and in a lesser degree so were Torbin, Tremayne, Malorum, etc) but it was a concept developed over time, and at first there were even some non Force users filling the role. Personally, I see no reason at all for the Inquisitors to be gone by the time of the OT. Nothing indicates they would dare crossing their masters and face the whole Empire for it, and nothing indicates that the Sith would willingly dispose of a very powerful tool just when the Rebellion is growing stronger than ever. They should keep them around to act as a counterpart to any Jedi (or even darksider) willing to plot against them, whether within the Rebellion or by themselves, like Maul. For me the most logical solution is that Vader doesn´t train Inquisitors anymore, so the ones that fall are not replaced. We really don´t know their numbers, but both the 7th sister and the 8th brother talked about a not so small number of Inquisitors left... so, while I´m not sure if this would be an option for the writers at this point, to me it would make sense that when the Sith are gone, the remaining Inquisitors slowly end up becoming or having some kind of influence in the founding of the Knights of Ren... About Jerec, I can´t agree more with you, I would love to see him in canon, even if I get the feeling that he is very different from what they are showing us now. Jerec was even a governor, with great political power and with many personal goals that didn´t really held the Sith´s best interest at heart, while current Inquisitors are so loyal that they even renounce their identity and are designated by a rank instead of a name. Still, I think there is a number of ways to have him as an Inquisitor in canon!