Yes Keiko, my first idea was that the player should be able to watch his other camera view in PIP window which could be switched on and off as you wish.
Then I realised that "camera position lock" option would be necessary as now they always jump back to initial position when you switch from one to another.
The "partner's view" option was only one additonal suggestion which is maybe technicaly difficult and I agree that you should have permision from your partner to be able to view his camera angle.
Anyway, I am very optimistic and I find this idea great for chatching the small details as you noticed, I like to enjoy the distant view of the whole scene but I also want to know what is my partner doing, I like to know if he pulled out and penetrated the other entrance...
Player should be able to :
1. play with same screen and with all behaviour like it is now
2. optionally lock the camera views after you set them so they would not jump back to initial position each time you switch view from cam 1 to cam 2
3. player should be able to toggle PIP option where he would watch his other camera
4. player should be able to optionally watch the other players main cam view only if the other player allows that
If the option "partner's view" is technically to demanding, I would be more than happy to just watch my other cam in PIP window if I want.