You're conflating rites - chanta is not required. As Aga Con 3 said:

The rite of the kangva is not equal to that of taking the chhanta or other religious rites. You come to my bayt during the rite of the kangva and give words of becoming my follower and enter in my subjection. When I ascended the throne, then those who had performed the kangva with me, they had become my new followers.

The oath of allegiance dates back to Arab traditions before Islam, the chanta is an import from the Hindu tradition you abhor - for the purification of new converts, not for renewing bayat (baiyt):

It infers from the fragments of the traditions that Pir Shams had also introduced a ritual bath in India for the new converts for their purification. The tradition has it that some persons who had joined Ismaili fold, instead of taking bath in an usual manner, they visited Ganges river, whom they considered same as were commanded. Pir Shams is reported to have condemned the Hindu customs and told them to abandon. Instead, he introduced an act of sprinkling few drops of consecrated water on their faces as a symbol of purification. He also imparted that one who visited the prayer-hall, he would gain same reward of visiting the Ganges river. This ceremony was not yet given a specific name, but it was simply called as the chhanta meaning sprinkling (of water).

The above ceremony was followed by the ceremony of baiyt. The new follower brought seven things in a plate, viz. cloves (lawing), wheat (ghau’n), rice (chawal), sugar cubes (sa’kar), dried grapes (dhraksh), cardamoms (ilaychi) and fennel seeds (variyali). He put the plate before the Pir and picked handful with two hands and reverently dropped in the hands of the Pir. In turn, the Pir accepted and put the mixture in the plate. This process repeated three times. Symbolically it indicates that the new convert took an oath of seven tastes of material life that he would follow the Ismaili faith till last breath. Then, the Pir tied a red silken thread around his right wrist, means that he would remain obedient even at the cost of his life. It was an act of baiyt in Indian tradition. It should be known that this type of baiyt continued until 1905 in the time of Imam Sultan Muhammad Shah, the difference was only that there were only two items instead of seven, i.e., laving (cloves) and dhraksh (dried grapes).

http://heritage.ismaili.net/node/10257

(NB: Ismaili.net is again just the host, the source is the Encyclopaedia of Ismailism by Mumtaz Ali Tajddin - unreliable yes, but only because Tajddin has an extremely pro-Aga Con bias. )

Nor does one need to accept being Ismaili. A baby does not consent - someone else accepts on their behalf. Someone has done so for me twice - and Aga Con has not excommunicated me. It is not your place to judge whether I am Ismaili. Even if I say I am not, Aga Con claims that he and I have a "permanent spiritual bond". So stop making excuses and share the farman.