I perfectly understand but you could still move them a little to the back using the perspective idea (^), the area you would be using is the same, you could place the large stem plants in the back of the driftwoods, tall broad plants in the corners of the back to fill in some nice space you will have there and in the center back a nice plant like an Amazon sword would look amazing, and with the driftwoods pointing at it would all look great. Then in the front any small plants you like so you could appreciate the driftwoods and the plants in the back. But again that's just me.
what would you suggest doing with the rotala? moving back a bit farther towards the corner? If I rotate the piece on the right the way you suggest the space behind it will probably be taken up by the crypt. As for the piece on the left, there will be the space in the corner and the space directly behind it (more towards the center). I assume I'll put the rotala in one of those spots. I know my LFS don't have a ton of live plants, but I'll see what they have in terms of "tall broad leaf plants." I know they have sword plants, but other than that I think they're rather slim pickings.