Hi Jerry,
Not sure I can add anything useful, except for that freshly ground is always best in my experience. If the takeaways and restaurants use bought in cumin powder (realistically yes I'm sure they will) then I'm sure they will choose a good brand, and get through it quickly (nothing stale). But then are you saying that to aspire to BIR food you should copy that and not bother grinding cumin seeds ?
Surely, it can be forgiven for us amateurs (with more time on our hands than the hectic work of a BIR chef) that we grind spices to achieve the best freshness. After all, without wanting to appear sexist or in any way racist, would the wives of the (mainly) Bangledishi chefs cook meals for their husbands with less flavour than necessary, or indeed said chefs being satisfied with less than perfect.
I say grind away.
Regarding leaving out Cumin from Mix Powder.... Personally I find it's essential for that earthy almost 'sweaty' flavour. I know you're not a fan of cumin, and use it minimally, but this goes to show how each of us has different tastes. The best Restaurant Madras I've tasted (and have you at the Hilal) was not to your taste, but for me was Utopia on a plate.
No Sanity Check required, just a case of personal preference. Good analytical post though, gets the intellectual juices flowing.