Nationality is rarely based on race. Its based upon where you are born, or in the case of ethnicity, where your ancestors or older living generations were born.JEWISH INDIAN OR INDIAN JEW?
1) The question of observant or non-observant does not arise since the term Jewish in this specific sense indicates a racial type and hence those of Jewish ancestry have a distinct genetic makeup that differs from other religious types like say the Hindu.
2) Jews of different races have intermarried for generations giving rise to a common gene pool.
3) With the Hindu, however, marriage is strictly governed by the laws of eugenics that seeks to weed out abnormal practices like the incestuous type or the hypogamous kind and so the Hindu genome though distinct varies from say the Jewish genes which is almost completely perverted due to incest/hypogamy.
4) People of peculiar beliefs who inter-marry for numerous generations develop a specific genotype and this is their race-based ethnicity.
5) The term nationality is broad and may refer to people of diverse genotypes residing in one nation - the various genotypes may intermarry provided religious laws do not forbid inter-religious marriages but in most cases most people marry within their own religious community that may be comprised of different genetic types that get stirred together forming a kind of genetic potpourri.
6) So, can a person be a Jewish India or an Indian Jew is the question? Doesn't either term indicate an oxymoron? Yes, if the religious community is homogenous in genes formed by marriage among the adherents of various genotypes of the same faith over generations. Whereas, if nationality is a product determined by common genetic lineage, then one cannot be a Jew and an Indian simultaneously since both are specific genetic types. In such a case, the person, in genetic terms, is simply a Jew and not Jewish Indian or if he wishes to identify with his nationality then he's simply an Indian or an Indo-Aryan or whatever and not a Jew. As such, when seen in this particular context of genotype, a person cannot be both - Jewish and Indian - at the same time. It would be a contradiction in terms.
6) Interestingly, most Muslims in India are Hindu converts to Islam and if there's been no mixing of blood with Arabs, Turks, Mongols and Afghans then the gene pool of Muslims in India remains Hindu by nature, or is it so? See, Hindu converts to Islam have married among themselves most often in incestuous and hypogamous unions and besides their pattern of thinking and customs molded by the new faith have left an indelible mark on their genes and in this respect the Muslim genome in India will be after many generations markedly different from the Hindu one.
8) If nationality is not race/genetic based then nationality is a superfluous factor and in such a case a person may describe himself as a Jewish Indian, Muslim Indian or Hindu Indian provided he puts his faith above nation.
Dont kid yourself that there are not Arabs in India that are as Indian as your Hindus. What makes them Indian isnt some bloodline but their birth in the modern nation-state.