I have not yet seen Holley's paper in Science, but I think I follow most of what you say.
It is an old speculation that the S-RNA is so big because it may have to make a rather nicely balanced configurational change.
However, it was assumed that this would come about when the amino acid was added. Your idea that it will only happen when
the S-RIA combines with the correct codon is new to me.
I don't feel that there is anything hard to explain about the "Bernfield-Nirenberg" binding. You only have to
assume that in addition to the binding energy between the codon and the anti-codon there is a weak general binding of S-RNA
and codon to the ribosomes. I suspect that the binding between the codon and the anti-codon without the ribosome is too weak
to be observable at all easily.
Basically I think your idea a good one, but it may be hard to prove it.
Letter from Joshua Lederberg to Francis Crick (March 24, 1965) 
