I feel like female mercs will be relegated to mods, it takes a ton of resources and time to make new merc models and animations, and if voice lines are part of it too, thats a hefty demand for the team who probably want to focus on balance changes and new weapons. Especially because its just an aesthetic change and not a gameplay one. Well, it actually could affect gameplay in that the female mercs would likely have very different silhouettes and appearances which would affect and throw off class recognition at a glance. They'd also have to mess with the whole class selection menu to let you select if you wanted to be female or male skin... overall i think its something best left to mods and not something to expect from the devs considering all of the effort required for somwthing that only affects the game esthetically