No BIR base unfortunately - only a finished madras curry sauce inc oil which i compared side by side with my latest base (oil reclaim/extended cooking) and std LB madras.
i think u're right on the main 4. i'm not sure on the garam but agree it would need to be a very small amount.
what surprised me was that if u knew nothing else and tasting both the BIR sauce and oil u would say there is only onion, tomato, paprika, turmeric, chilli present.
the trouble is the taste that u would get from onion, water and tomato alone does not suggest the missing bits are solely paprika, turmeric & chilli. you feel there is something else but definitely not pungent or discernable - more like a collection small.
for this reason i'm thinking small qty garam or wholes spices (something like cardamom and bay).
i'm aiming for a back to basics approach as i know (from the bases i've tried) once this basic taste/texture is achieved the icing can be added (ie carrot etc). the onion for example in the BIR stood up like soft peaks where as mine does not - this is the 1-3 part "technique" but hopefully gives you a feel of the level of basics that i'm targeting.