Birthright pc game was one of my favourite pc game,but in the pc game's history was a flop.
I think that there are 3 reasons
1)lack of funding
2)poor adventure mode
3)quite good battle mode,but lack of units

For "heretic" birthright pc game I invite you to compare Dune 2 with Dune books.If Dune is considered an excellent book, Dune 2 one of the most important pc game of all times.Some heresies of Dune 2 weren't important like the change of the story,but other were fundamental...like the big arsenal for every faction and their special weapons (there aren't in the book).
So I think that in a future birthright pc game you should have a vast army selection (in the gorgon's alliance for example dwarves have only archers and infantry,human were more various but it could be better) for every race,maybe some military technology (like more powerful sword),and obviously at least a special unit for every faction.
From the other hand the political mode of gorgon's alliance was great for the times and needs very little improvment(and not heresies here).Of course you should play with all Cerilia and not only Anuire.
I think that a pc game with all this improvments shouldn't be refused from a wise softare house...


I'm regret that I can help you very much....I can only makes game with rpg maker 2000!