The other way to read the "it'll be hard to miss her on the battlefeild" is that it has more to do with her being "Shiva's Dominant" than with her being a woman. The summons in this game are not... subtle... in any size, shape or form. If someone is summoning a Shiva as tall as a ten-story building (or transforming into her more like it), then that's going to be really obvious on a battlefield. And low and behold, the next frame is Shiva getting in a fight with what looks like Titan with everyone scrambling around beneath her.
I really wouldn't take FF7R as an example as how Square is going to handel this. FF7 had a lot of... controversial portrayals of things by today's standards that would have to be thought about. FFXVI is being made from whole cloth. Also, looking at the other games this creative team has put out before and what kind of stories the rumored scenario head has worked on, they have a very good track record with writing non-passive female characters. These are the people who gave us Y'shtola, Alisae, Kann-E, Nanamo, Merywybb, Ysalye (Iceheart), Yugiri, Fordola, Yotsuyu, Ryne, and countless other female side characters who aren't doormats for anyone. There is going to be strong female characters, we have just seen zero cut-scenes relative to the overall length of a 40-60 hour game.
Judging the gender split for FFXVI based on this trailer is like judging the gender split of FF7 based on the trailer that only had bits and pieces of the bombing mission in it. We just knew what the cast of FF7 was going to be before seeing that trailer, so no one bothered mentioning there was only one girl in it. Like seriously, can you imagine what people would have said about FF7 in regards to gender ratios if the first trailer they got of it was bombing missing footage that was designed to hide all of the main class except the main character? And they had no idea what the rest of the game would be about yet?