Can you elaborate more on this? I don't see why would they be weaker.
Modern India works as well as it does, to the extent that it does, by being relatively limited in its frontier territory, and, excluding Kashmir and Jammu, that frontier territory either being Hindu, animist, or Christianized. Excepting the Nepalese, Tamil, and some of the Zomi people, its ethnic divides are almost entirely internal. I'd argue that India would do fine with Muslim majority Bangladesh, due in large part to historical and cultural links to West Bengal, and the still significant Hindu and Buddhist presence in the former East Pakistan. Sindh, with its historical links to Rajasthan and Gujarat might do fine, especially without the population transfers triggered by Partition. Pakistani Punjab is a bit dicier. Should the province keep its borders more or less pre-partition, you'd have a state approaching Uttar Pradesh in population, and, therefore clout, with a Muslim minority in the heart of a mostly Hindu country. The communities can, do, and have gotten along, but the religious strife that has occurred in India in OTL could be greater, and weigh more heavily in the politics of the Union. This leaves alone the total basketcases that would be Balochistan and Khyber Puktunkwha (then divided I know) that are susceptible to manipulation by charlatans and religious extremists in OTL with those areas in a state that is constitutionally and overwhelmingly Muslims potentially feeling greater alienation under the secular. more Hindu-influenced rule of further away New Delhi....
