First I must point out that for all Eamon's talk of a surviving son of the blood, most banns do not care about Alistair's stronger claim to the throne even over a "commoner" like Loghain. If the Warden does not destroy Loghain's support, the banns side with him, because he displays strength. They will also accept Anora over Alistair.
Second, the question of how influential Mythal/Flemeth were is an interesting one. She killed Connobar, which allowed his Cousland general to take control. But it was said that Connobar had no heirs. So perhaps this change was inevitable. The story also goes that Connobar bargained with money he did not have. So perhaps the Couslands were always destined to take Highever. Flemeth just played a small part by becoming part of the Cousland's destiny, rather than being the cause of it. Same with the Warden treaties. It is better to have them than not, but none of them were really needed. Everyone who agrees to help you can do so because you helped them with something. The only time I remember using the treaties was to gain access to Orzammar, but theoretically, having Shale with us could have been enough since they would want to record Shale's existence in the memories. I suppose getting us out of Ishal is a pretty big role. But would we really have died had she not intervened? Or was her intervention part of the reason why we lost consciousness? She needed a reason to put us in her debt so we would agree to take Morrigan with us. But I guess she did help Maric and Loghain.
Not exactly sure on how old Fergus is now, but I estimate around 40 something.
Well, World of Thedas Vol. 2 has a story about Bryce and Eleanor that contradicts the lore in Origins. I don't consider the story canon, but who knows what BioWare will do with it from this point. Basically, Bryce and Eleanor don't even get married until like 9:03 or something. Which means the earliest Fergus can be born is about 9:04. So that would make him 40 in 9:44. But it would make him 26 in Origins, which just doesn't seem correct. He looks older.
However, WoT2 is wrong compared to the lore and facts stated in Origins. Bryce and Eleanor must have been married during the Orlesian occupation, and I believe Fergus was born during it. I estimate Fergus was born in 8:95 or so. That would make him 35 at the start of Origins. 35 seems right. Bryce and Eleanor are also pretty old. Figure about 55 for them. Rendon's Howe's eldest, Nathaniel, was born in 9:01 I believe, and Rendon was another old dog. Figure they fought in the war in their late teens, married in their 20s. That puts them at the right ages in comparison to their kids. Loghain is another one. He married and bedded Celia by 8:99, and Anora was born 8:100.
I calculate my Cousland as being born 8:99, for any who are interested.
He more then likely has remarried and sired a new heir to Highever, and hes clearly much younger then Teagan and Eamon, so I don't see how theirs any negatives to say he weak and people wouldn't want someone like him as King lol.
WoT screws up Eamon and Teagan's ages too, though I don't remember how badly. Basically it makes Eamon much younger than he looks in Origins. Also, it wrongly states that he left Ferelden and stayed out of the war, when Origins clearly shows Loghain saying, "You fought with us once Eamon, you cared about this land once. Before you got too old and fat, and content to see what even you risk."
But yes, Fergus should be younger than they. Eamon at least.
Sorry for the rant. At least I quoted the right person this time.