If you break down the "process" you have
Intent - accidental, negligent, reckless etc
Contact - low, medium, high
Impact - none, low, medium, high
JT was deemed negligent,high,high
According to strict wording of appendix 1 contact is "high" (despite the tackle being below shoulders)
Impact again by definition was high because he got concussion
This leaves intent as the only aspect that is technically arguable
If they can prove accidental then the other aspects are mute and he gets off totally
I think that this has to be the main argument of the appeal
(unless they are allowed to discuss fairness of the rule wording, specifically appendix 1)