To clarify the original points about the conference;
If Riou and
Teresa die, the 'game is up'. The other leaders are either ineffective as a 'front man', i.e. the Mayor of Two-River, or are strategists who need others' charisma to play their hands (i.e. Shu, Apple). Riou is charismatic and a great figurehead due to his connection with Genkaku. Teresa is well liked and a fantastic leader, plus she has been passionately fought for and much has been sacrificed to secure her. These two die, I think the effect on the Dunan Army won't be to galvanise them into revenge a la
Highland, as Blight declares, but would be to deflate and exhaust them. Who is left when Riou and Teresa are gone anyway? Ridley?
Nobody else has their credentials, respect or charisma. Sure, Riou sucks as a leader, but as a figurehead puppet being utilised by Shu, he's got a lot of mileage, and same goes for Jowy with Leon. But if Shu and Leon don't have their puppets, they become useless. This is why Mathiu, Lucretcia, none of them became 'leaders'.
So in that sense, it makes good sense for Jowy and Leon to try and facilitate a scenario where Riou and / or Teresa could be lured over and / or die.
If Riou had accepted Jowy's offer, I doubt Jowy would have had the brains to have considered the possibility of accusation of plotting together. Leon wouldn't - he's an excellent strategist but he lacks any kind of social skills, and I'm not sure that kind of social / civil psychology would be his strong point. He's good at winning battles or manouevering through the political atmosphere; this might just be out of the realms of his thinking. Aaaaaaand, of course, Leon is not the best
. He clearly isn't - Mathiu was better. And Leon looses the Dunan Unification War to a failed disciple and someone who isn't even a Silverberg. So factoring that in, I'd say not all of his decisions are water-tight anyway! This could just be a massive mistake for him.
who isn't trying to be too harsh on Leon - Leon is his second favourite character, after all.