I see no practical use of Nepal Sambat, because it was only common in Kathmandu as many of you have pointed out by mentioning the lalpurja, and other things. But they are our cultural things specific to certain group of people only. I agree to keep the culture alive we need to practise it, but not to the extent of segretating Nepali people. BS has been going pretty well, I have heard no complains about it, if I am mistaken do correct me. When one system is running smoothly I see no reason why it should be changed. As as being from a newar community myself, I would like to question how many of Newari people even know how to speak proper newari, how many of us know how to write in Newari language. So if you really want to preserve the culture I guess its better preserved in terms of language and lipi rather than just a date which other nepali people are not easy with. I also bet even if it were made official with BS as official, it would be very few people who use it. And also for official purposes you would want something that everybody is easy using it. I would advocate for newari language to be offered as an optional subject in colleges as a part of plan to save the newari culture rather than try to make Nepal Sambat official. What do u think?