Don't agree with any of what you've posted. Also, they could be visible during exploration as I mentioned earlier if this would help with immersion.
Xenoblade has tons of things on screen, even during battles the world and the monsters are still "there", as you can see when a big monster starts attacking you and you can continue running away, with everything still visible.
Previous games had 4 party members; this has 3, plus companions, so the number go up from 4 to 6
If 2 more players during battles is in your opinion the issue causing frame rate problems (in a non final build, and with previous games still not being optimized at a firm and stable frame rate in every occasion in their final builds) I don't know what to say
They (Blades) being additional element on screens creating a more crowded image alongside enemies and HUD is true, on the other hand, of course.
Still, they are prevalent and I really appreciate to see them also in their humanoid forms and not only as weapons. They are a crucial part of everything in this game.
You'll probably discover it later, I can't comment further on story elements in this moment.