Giving a free GP with Buddhism or Hinduism would be very, very unbalanced. I mean, really. Founding a religion is powerful, but what if they instead started a Golden Age? They would dominate their neighbors, and likely, the entire game for getting a GA so quickly. Plus, even if they did use it to founda religion, how is that any different from simply researching the corresponding tech?
Not to say I don't like your idea. It just needs some work. Maybe researching (not trading for) certain technologies could give a boost your GPP, relative to the technlogy and how many GPP you have already spawned. This way, if two civilizations research say, Polytheism, they both gain a large sum of Prophet GPP, but the first one to spawn a GPP (either through wonders like the Oracle, priest specialists, or researching other religious technologies) will likely found the religion. Because founding a religion consumes a Great Prophet, a Temple and Monestary should automatically be built in the founding city, allowing, among other things, the immediate construction of missionaries and priest specialists.
This accomplishes three things:
1) The civilization that founds the religion would generally be more religious then the one that researched the technology first, giving more religions to pious leaders and less to tech-whore leaders.
2) Players can chose to found their religion in certain cities, most often one in need of culture or a more religious city, rather then having it spawn in a random city on your border that Montezuma captures next turn.
3) Players have more incentive to research their own technologies for the GPP boost(This would be applied to all technologies, not just religious ones, so Construction for example will help spawn a Great Engineer), rather then steamrolling ahead and trading their shiney new technologies for all the ones they didn't research.