GTA V isn't anything like Bioware games. A major part of Bioware games is the connection you develop with your party members, which GTA doesn't even have. And again, it's a linear plot. You don't make wildly different decisions in world, you don't get multiple personality options. Every conversation you have has multiple options to choose from, where with set characters they just say their line.
Let me explain it this way, every game starts out with a word budget. Usually, the budget is spent entirely on one character and their dialog with their companions and NPCs in the game. There's not going to be extra words that come about for dual protagonists, they just get what they get. The only way for it to happen is to split that budget up more than they usually do. That's literally the only way for this to happen. Each protagonist will get less than they would have in a normal, one protagonist game. So, they'll have to make cuts somewhere. You'll get less scenes with your party members for each character, or they'll cut things like the interaction with Scout Harding in Inquisition. It can't come from nowhere.
This isn't a question on RPG vs not. It's about resources.
There is no strict word budget. Motion capture, coding, animation, and directed scenes and levels cost way, way more than merely some lines (words), sorry writers. To that end, Inquisition didn't spend very much, if any, resources on varying the animation, cut scenes, the MEAT for the different backgrounds of the Inquisitors. There also aren't any choices beyond the specific race-related war table missions that pertain to the different races. Seriously, look at the major choices that would be imported from DA3 into DA4. Which of those pertain to race? Close to none if not none.
Assuming they continue to only vary the words - not actions, choices, direction, scenes, animation, literally any of the resources worth writing home about - based on what race the Inquisitor was, there is substantially no great additional expenditure needed. It all comes down to the partitioning of the script between protagonists. It'll be the same length of game, therefore same overall amount of resources. Secondly, this won't impact the connection you develop with characters. Especially if, as I said, the inquisitor's part is not 50% of the game. The companion-recruiting and managing would still be left to the new protagonist.
The inquisitor could even be a companion for that matter. One who gets one or two missions they themselves control ( remember we already are able to control companions technically in all other games).