I recall reading a discussion of Patricia Gray’s dramatic adaptation in 1968 of
The Hobbit years ago in a fanzine. The author of the review, like you, had a very lacklustre opinion of the play but noted that the replacement of the Elven King by an Elven Queen may have been inspired by a wish to expand the possible female roles in what was a children’s play to be presumably mainly presented by school children.
That Tolkien himself authorized the play means nothing, save that Patricia Gray had made financial arrangements with Tolkien and Allen & Unwin which were sufficient to compensate for any qualms that Tolkien may have had. Of course a published play based on a copyright work must have permission of the copyright owner of the original work to be published legally.
I presume similarly that Tolkien ‘authorized’ the dramatization of
The Lord of the Rings on BBC radio, but Letter 175 in
Letters of J. R. R. Tolkien shows he found the results distasteful. The same goes for various translations of
The Hobbit into various languages, some of which he later expressed his distaste for.
Those who wish may view a complete version of this play on the web beginning with
https://www.youtube.com/watch?v=m8c0Bp3h_Ds.
In the year before authorizing Patricia Gray’s play Tolkien had also authorized a musical version of
The Hobbit scripted by Humphrey Carpenter (
https://en.wikipedia.org/wiki/Humphrey_Carpenter) and presented at New College School in Oxford. See
http://tolkiengateway.net/wiki/The_H..._adaptation%29,
http://www.bbc.co.uk/programmes/b01ld15z, and
https://en.wikipedia.org/wiki/Adapta...s_and_musicals. See also
http://www.operanorth.co.uk/blogs/i-gandalf,
http://www.cornishguardian.co.uk/Hob...ail/story.html, and a modern production described at
http://www.theaterforkids.net/press_hobbit_camera.htm.