I'm really interested in hearing how this mix powder turns out.
Regarding Paprika, I'd say it's there predominantly for colour, it just doesn't add a lot in terms of flavour in the quantities generally used in mix powders. Used in large quantities obviously it does.
Turmeric is used a lot because it's cheap and and aid to digestion I suspect.
With regards to your mix powder, I'd probably make Coriander and Cumin the two largest components followed by ground fenugreek. I'd make those 3 represent 1/2 - 2/3rds the entire quantity. Coriander I think has to be the largest component followed by Cumin and then fenugreek. Perhaps in a 4:2:1, or 3:2:1 ratio.
Presumably the gram flour is there for thickening?
The remainder I'd make up from turmeric, mustard seeds, curry leaf powder and asafoetida, with the latter being the smallest component of the lot as it's quite powerful.
That's probably where I'd start from.