I can see why Bioware decided not to implement this idea, but I'm a bit disappointed as well.
For one, what would stop the Inquisitor from taking the Sunburst Throne for himself/herself? Keep in mind on how just how devastated that the Chantry leadership, organization, stability and overall existence was badly damaged or outright made non-existent by many factors all piling on each other at once such as:
The mage-templar war (With the vast majority of Mages, templars and seekers refusing to recognize Chantry authority and abandoning it);
The Divine's sudden death along with that of any immediate successors or several leaders/delegates from the mages and templars willing to reach a compromise due to the Breach;
How much power the Inquisition can gather for itself via recruiting the templars/mages and grey wardens, Establishing positions and routes of trade/espionage/supplies throughout Orlais and Ferelden, Earning the support and patronage of various nobles and organizations including the King/Queen of Ferelden and the Empress/Emperor of Orlais who either owes a giant debt to the Inquisitor or the Inquisitor has so much blackmail on them that they pretty much control the emperor/empress like one would a puppet on strings;
Not to mention the rising number of people who would actually support the Inquisitor's bid since many believe that the Inquisitor is basically a messiah blessed and sent by the Maker himself. (Something hugely helped by how the Inquisitor can single-handedly close/open close rifts in the Fade, Slew a pseudo-archdemon; Closed the Breach; and single-handedly killed one of the original Magisters who caused the Blight and the birth of the Darkspawn)
If the Inquisitor wanted the Sunburst Throne for himself/herself, who would stop them? Is there really any legal or ethical grounds that can be argued to oppose the Inquisitor's bid that can stand up the man/woman's deeds and their literally apparent God-given power? (Most people don't know the truth and it's up to the Inquisitor as to whether they'll reveal it or not)