Is he unsackable? Why does anyone even think that? How many top teams have sacked a coach when in the mix at the top in English RL, it might happen in football but not this sport.
I do believe however some thought should perhaps be going into who will be next in line (perhaps it already is for all we know) as next year will be McDermott's 5th which is quite a while nowadays and possibly should be his last.
We've seen however with the Powell-Smith and also McClennen-McDermott "changes" that we try to do things a certain way of 'passing over' rather than just saying "you're sacked, he's a new guy" although to be fair they might as well have been for all intents and purposes
As for an assistant YEP had this after Lowes was confirmed to Bradford....
YEP wrote:
Meanwhile, McDermott –who is currently assisted by under-19s boss Chris Plume and Hunslet Hawks coach Barry Eaton - confirmed he hopes to appoint a replacement for Lowes. He said: “We are and we have been looking, but it’s worth mentioning that Barry and Chris is working out very well. It is something we will continue to look at.”
So they have apparently been looking for someone, just haven't found the person whose the right fit and I'd rather patience was taken with any appointment rather than rushed simply because we don't have an assistant.