I recently learned that the priest of the Vishnu temple in my native village of Poondi is a low-caste person. The notion of a low-caste person serving in a temple didn't surprise me, since in the Sri Vaishnava sect it's a well-established practice for low-caste people who have performed Sharanagati (complete surrender to Vishnu) to perform service to temples. But I was more surprised to learn the priest was not a Sri Vaishnava, but rather a Vaikhanasa.
As I discuss in this answer, one of the early movements that was important in the development of Vaishnavism was the ancient Pancharatra movement, whose sacred texts consisted of detailed procedures to worship the sage Narayana, an ancient incarnation of Vishnu. Since the Pancharatra texts originated from Narayana himself, they are followed by pretty much all mainstream Vaishnava Sampradayas, whether Sri Vaishnavas, Madhvas, Gaudiya Vaishnavas, etc. But as I discuss in this answer, there's another group of Vishnu-worshippers who worship Vishnu according to the different set of texts, the Vaikhanasas. Vaikhanasas place more emphasis on rituals than in high-minded philosophy; while mainstream Vaishnavas are committed to elaborate Vedantic philosophical systems, like Dvaita or Visistadvaita, Vaikhanasa doctrines are more about the construction and worship of idols and the like. The vast majority of Vishnu-worshippers follow Pancharatra, but there are several Vaikhanasa temples in India, including the world-renowned Tirumala Tirupati/Venkatesshwara temple.
In any case, it seems that the priest in my native village of Poondi belongs to the "Bhattacharya" community, which is apparently a community of low-caste Vaikhanasa priests. My question is, are there any sources that discuss this community? And assuming this community does exist, what is its origin? As I discuss in this answer, the Vaikhanasa system was founded by the sage Vikhanasa, who taught it to four sages, Atri, Marichi, Kashyapa, and Bhrigu. And Vaikhanasas believe that they're "Garbha Vaishnavas", i.e. that the child of Vaikhanasa parents is initiated into the system by Vishnu while they're still in the womb. So how could a system which began with four Brahmins and which believes that only the offspring of Vaikhanasas can be a Vaikhanasa ever acquire low-caste members?
And is true that the Vaikhanasa system allows low-caste people to be priests? My understanding is that of the two systems, Pancharatra is a bit more liberal on caste than Vaikhanasa; Wikipedia says this:
With the rise of the Shri Vaishnavas the Vaikhanasas declined in their temple role. Rāmānuja, leader of the Shri Vaishnavas and the first organiser of temple administration at Srirangam Temple, replaced the Vaikhanasa system of worship with the more liberal Pañcaratra system, expanded the fivefold division of temple servants into tenfold, and gave an important part in ritual to sudra, lowest caste, ascetics. This change spread to other Vaishnava temples.
And judging by this excerpt from the Vaikhanasa Dharma Sutras, their views on the caste system seem to be perfectly orthodox. So how could the Vaikhanasas accept the Bhattacharya community and allow them to be priests?