If you're going to respond to me, please address what I've written, instead of posting baseless dismissals. Let me break it down for you:
In video game development, "expense" primarily exists in two forms of currency: time and money. For a flagship AAA game like Assassin's Creed, wherein a yearly release is mandated, time is the less frugal of the development currencies and thus the limiting factor.
In terms of raw asset creation, throwing man-hours at the problem has diminishing returns due to the nature of artistic design and quality standards. Concept work and design, construction, iteration, implementation, testing, quality control; every step takes time to make sure the overall quality bar is being hit. To add a female player character, Ubisoft's team would aim for the highest level of quality, and thus spend the maximum amount of time on the feature. Their pipeline would most likely create an agile construction process, but at the end of the day, it just takes a long time to make AAA quality assets.
For a female character, every wearable piece of clothing would need to be hand created, textured and animated from scratch to look and feel correct, and to hit the quality bar set by previous games. Assassin's Creed employs a combination of key frame, mo-cap and procedural animation. This allows for the smooth animations we've come to expect from the series. There would of course be some degree of overlap, especially within the procedural animation area, but the mo-cap wouldn't work at all, meaning every mo-capped cutscene needs two versions, and a lot of the key-frame would need to have gender specific variations. And then it all needs testing.
This would get the female character into the game world, however specific interactions with the NPCs would require another layer of customisation. Unless procedural animation is employed for all of the NPCs - which it isn't - their animations for interaction with the player characters would need to take the gender - due to the different models - into account when animating. Again, there is of course overlap, but a good portion would need to be redone.
On top of this, script and voice acting needs redoing from the ground up. All game events and NPC dialogue needs to be gender neutral, to minimise the amount of variation. And then the entire dialogue for the player needs to be re-recorded by a female voice actor.
All of this additional work results in a potential - and even then a small - increase in sales, assuming they push the character customisation heavily in their marketing, to combat the perception that Assassin's Creed is a "boys" game. So, hopefully you can appreciate the amount of work that would go into it.
Comparing Assassin's Creed to Mass Effect is also kind of dishonest: the animations in Mass Effect were serviceable but not in the same ball park as Assassin's Creed, and even then they still had a number of gender specific animations.
...this whole cost-driven argument coming from a bigAss company is bullshit. Adding a woman or a gay character is a burden for them...
Exactly! That's why Mass Effect crashed and burned, all Bioware RPGs failed, Tomb Raider isn't a series, character-driven MMOs aren't made, an- oh wait. The opposite of that is true.
Now, you certainly have a point about gay characters. I entirely agree with you - they're scared of the potential sales ramifications. And that's pretty shit, frankly. But you've lumped women into that argument egregiously. As I explained above, return of investment is a massive factor. It's simply very expensive to add female characters at this level of production, and unattractive to large companies because it doesn't increase the sales in proportion to the cost.