Instead of attending a conference on female ordination Ajahn Brahm decided to preempt and upstage the conference by ordaining a few of his female followers. In so doing he has set back the cause of female ordination in the Theravada by many years. How could he possibly have imagined that he was single-handedly qualified for such a task? In this light his recent attempt at a light-hearted 'monk for sale' campaign is indeed amusing, but not in the way that he intended.
There is scriptural support for what he did in the Nikāyas and also the Āgamas. He was within his rights to ordain bhikkhunis in the absence of Theravadin bhikkhunis. He did not need consent from the Thai sangha or anyone else for what he did. He was well within his rights and I believe he was well aware of this as well.
In any case, he is promoting Buddhism primarily in Australia where women are legally and culturally entitled to equal rights, which means they can and should be able to receive a bhikkhuni ordination regardless of whatever the sangha administration in Thailand thinks.
As far as altering the Theravada tradition is concerned, 1928 is only yesterday. At the very least one has to wait until the current generation of elders is replaced. In order to give a renewed female ordination lineage credentials that cannot be questioned there would also have to be a Theravada-Mahayana Buddhist Council on the subject. This process could easily take another decade; perhaps longer now thanks to Ajahn Brahm.
Why should the current generation of elderly monks in Asia have any bearing on women in Australia and elsewhere who want bhikkhuni ordinations?
Thailand, Cambodia, Myanmar and Sri Lanka do not officially accept any of these ordinations as valid. There are signs of progress in Sri Lanka, and to a lesser extent in Thailand, but full recognition and acceptance are still a very long way off.
What does it matter if these Asian countries don't politically sanction ordinations, especially in countries like Australia? Women have the right to be ordained as bhikkhunis. Ajahn Brahm was within his rights as a bhikkhu to ordain them in the absence of bhikkhunis.