Quote: "So if characters are controlled by DarkAI and DarkAI is hard coded into the engine, we are limited to what can be done in terms of making custom scripts for characters."
Not really because you call the 4 darkai controls in your scripts to change the players behavior.
Yes it is limited because in a sense being there are preset AI actions, but there are many ways to implement these actions with other FPI actions for various unique behavior.
Quote: "It seems a bit strange there are now features going into FPSC X9 such as melee and head shots which haven't gone into FPSC X10 yet. Why spend all that time on a new engine and then spend more time supporting the old one?"
Because X10 utilizes the latest hardware.
That is the reason to develop X10, and the same reason to support the older version. (not everyone has the latest hardware)
The x9 version is doomed in the end when Microsoft stops supporting XP, but until then improvements in X9 may help lead the way for improvements in X10.
Maybe it is easier for Lee to test his new ideas for the engine using the older one.
At the same time he is pushing these new changes to the masses because the old engine has a larger user base.
That way he can get more feedback and a better insight as to what the community thinks about the change before it becomes part of X10.
This of course these thoughts are a maybe as those are just my thoughts on it, so I could be wrong.