Shreejit,
There are a lot of things that are not clear. When you say the current JUnit report generated by TestNG is not very informative, I was wondering what you would be hinting at ?
The whole point behind TestNG providing you the luxury of building your own reporting mechanism was to circumvent this part and build what you feel is informative and according to your needs.
PS : I haven't worked on any of these so I wouldn't have samples to share. But if you can add more context, I could try taking a jab at this and see if I can build something.