Well, that's a given. The trick is to work with what you have and present choices and branching storylines which don't require twelve years of non-interrupt man work. I believe Troika's games had an optimal approach to this - every area presents a set of quests or situations which can be solved in several ways, but not many present such a branching complexity that would be detrimental to the game's development. Most quests are self-contained, and only some have later repercussions. Not only that, there still remains a mostly linear path to the endgame, even if at some point during that path you can 'change sides' or motivations, be it somewhat halfway (Arcanum), or in the very end (Vampire).
I'm sure this is expensive and taxing on resources... But honestly, so is full voice acting and other such features, if nor moreso.