The good UKY people in this thread have been very helpful, I think it's great. Possibly missing the point, I don't know. If I can just interject another thought for you all to consider.
In terms of overall strategy...
When they go for FLR and it reaches the DL stage, he will be putting his cards on the table about his mental illness, and that's an imputed knock-on to viability for employment and other types of things like that. Plus marginal finances. Plus a *very* flimsy ground for jumping queue.
If the DL is refused, all of that stuff is going to be in his file when he goes to the Tribunal, or for entry clearance, or even any other type of visa. And certainly from the Tribunal to the public domain. Their solicitor told them it's a 50/50 chance of success. Would any of that affect your views on overall strategy? How would you take those things into account in this early phase of strategy formulation?