Interesting post
adding some tandoori mix - yeah have tried this and works quite well but too much and it produces a tandoori flavoured curry (not surprisingly).
use of garam masala - I agree it doesn't bring one closer to BIR, probably further away I would have thought. Garam masala, in home style cooking, is usually added at the end, just before serving. Like mix powders, garam masala is a mix also, but tends towards more aromatic spices as cinnamon, cardamon etc and this may be why it doesn't have the BIR taste.