I am going to implement support of KML format in a while. You can put corner coordinates into KML and open it.
You can check status at #5451
Closing this issue as wontfix - I want to avoid complexness of PicLayer as much as possible, and one new dialog cannot help me with that goal. Sorry.
By the way, current implementation of Java2D does not support Perspective transformations, so only 3 corners can be fixed, not 4.
And the last - current PicLayer supports raper points so you can adjust picture in new way, without scaling and rotating a lot.