Christian,
You said,
"I've been exploring the considerably close ties between Blavatsky and Buddhism...."--> Blavatsky said Buddhism was the religion that is closest to the Ancient Wisdom. She did point out, however, that the two are different.
"...I was curious about the many Buddhist positions and views I come across in the SD and other works, sometimes to the exclusion and dismissal of other philosphies of Ancient Wisdom."--> Blavatsky teaches that all religions become corrupt as the centuries go by. Perhaps Blavatsky felt Buddhism has become the least corrupt religion over the centuries?
"The Mahatma ties to buddhism also underscores a preference to a select religion, as at least one Mahatma was a religious figure."--> I do not think so. I think it is a matter of Buddhism being the closest religion to the Ancient Wisdom.
"I was becoming annoyed in reading the Letters and other works, and being confronted with the word "conversion" too frequently."--> I have not come across this. Please feel to share some examples.
"My concern was, and is, is there an underlying intent to [actually] draw people to the Buddhist religion?"--> Blavatsky was adamant in saying she does not want people to quit their religion. Rather, she wants them to find the original teachings each religion has lost.
By the way, I was a Buddhist for many years, but I finally renounced Buddhism, because some key Buddhist teachings go against my belief system.
Your line of thinking does beg the question: what would a religion modeled on Blavatsky's Ancient Wisdom look like?
"Theosphical teachings have borrowed some concepts and terms from Buddhism."--> Blavatsky (and I) would say it is the other way around.
"Theosophical writers have also interpreted some Buddhist teachings in unorthodox ways."--> Hallelujah! This is the very reason for Theosophy's existence.
" Some theosophists like Blavatsky, Helena Roerich and Henry Steel Olcott also became Buddhists."--> Blavatsky and Olcott are said to be the first Caucasian Buddhists in the history of the world. Olcott has been called a Buddhist hero.
The White Buddhist: Henry Steel Olcott and the Sinhalese Buddhist Revival"Tibetan Buddhism was popularised in the West at first mainly by theosophists like: Evans-Wentz, Alexandra David-Neel."--> Theosophy takes credit for popularizing ideas like reincarnation and karma in the west. I feel Blavatsky started the entire New Age movement, way back in the 1800's.
"Blavatsky sometimes compared Theosophy to Mahayana Buddhism."--> There are many commonalities.
"But the schools of the Northern Buddhist Church…teach all that is now called Theosophical doctrines, because they form part of the knowledge of the initiates..." --> I agree, except for the part about "all".
"Undoubtedly Madame Blavatsky had in some way been initiated into the deeper side of Mahayana teaching and then gave out what she deemed wise to the Western world..."--> And I am grateful for her having done this.
"Here is the real Mahayana Buddhism."--> I agree.