I wish this forum had multi-quote.
Danny Boy 7 wrote...
Well that was just a bit of possibilities/flavor text for my argument lol. It's true sure enough that Tevinters don't like to share power and in that regard it's not hard to imagine that they'd use anything especially a potentially powerful unleashed rebellion in order to weaken Chantry/Templar/Andrastian forces or at the very least to get Templars the hell out of the Imperium.
The Tevinters don't *want* to evict the templars from the Imperium. The templars form a vital part of their army. If you pursue the "Investigate" options after attempting to give Fenris a Sword of Mercy, he tells you that the Circle of Magi (a Circle in the sense of a council, not a prison) controls both the Imperial Chantry and the Imperial Templar Order. It's possible that the Tevinter templars might want to defect to a land under the Orlesian Chantry if only to get a taste for how it feels when they are the ones calling the shots, but the Circle would attempt to hold on to them because a group of guys with swords and lyrium-imbued arcane abilities is not a bad weapon to use against the Qunari saarebas. Fenris believes that the Qunari are capable of leveling Tevinter, if that was their goal, and states that the only reason that Tevinter is at war with the Qunari at all is because they have been attempting to regain Seheron for the last few decades.
Just to play devil's advocado there may be two things you are overlooking. First off there is always the possibility that no one wants to trade...with either side. I mean everyone might pull a "Uh...you guys do what you want we'll be over here." unwilling to get involved out of fear of reprisal from the other side should they win. Now that's not to discount the Formari or what they create because afterall the Dwarves are major partners with them albeit it's been through the Templars/Chantry but will those supply lines still be viable now that they don't have that Chantry seal of approval. 
People will *always* want to trade with someone willing to sell them life-saving medicine. There might be a very few people out there who have elected to die because they have moral or philosophical objections to pharmacies, but this goes against human nature. People want to live, and the mages are the only people in Thedas capable of curing disease or healing injuries.
The second is that while there are definetily more mages, the Templars/Seekers are an army, have fought in wars or the defense of their nations etc while the mages are not.
This is factually inaccurate. The Chantry kept mages specifically to use as a weapon. The Fereldan Circle sent mages to Ostagar and later, to assist the Warden, if said Warden did not choose to annul the Circle. The Grey Wardens valued the military prowess of the mages enough to forge a treaty with them. King Maric ruled during a time of peace, but his Orlesian predecessor did not hesitate to enlist the Circle in their war effort against Maric's forces. Have you ever wondered why most mage spells are combat oriented rather than agricultural? It's because mages are trained from birth to be used as a military tool. Uldred is part of the elite council at Ostagar, along with the king, the general of the army, and the leader of the Grey Wardens, and he seems to have considerable say in how his forces are deployed.
The age and physical fitness of mages is irrelevant. Young, old or infirm, mages will fight for their lives. Their "challenge rating" is not affected by their age. A weak and feeble old man poses the same arcane threat as he did thirty years before. No, he can't keep up in a retreat, but his sacrifice would enable others to live.
It probably isn't constructive to think of the mages that elected to remain with the Chantry. They're dead. They would have been the first targets of Lambert's forces. The Divine might have wanted to protect them, but she is one woman. The Right of Annulment is the prerogative of the Grand Clerics, and not all of them would be shy about invoking it.