Finding 2 BNs per gamemode means you'll have to find 8 BNs in total to rank a std,taiko,ctb&mania set, which basically means the death to those large hybrids sets.
I think 1 BN for each mode, and one final BN from the main mode would be way better. That way you somehow 'incentive' other gamemode sets which isn't bad at all in my opinion. Also you keep the procedure of checking every gamemode properly.
Now the question is how you define the main mode of an hybrid set. The one which has more difficulties? The one which has the hardest difficulty? A mix of last two?
EDIT: Another idea that came to my mind. What if a 'main mode' on hybrid sets is valid when that gamemode has at least 1 extra difficulty or higher (or maybe ~4.8* +)? That way you can have multiple 'main modes'. That would mean that hybrid sets with a lot of harder diffs for each gamemode will need multiple BNs, but I think it's fair enough because those sets are the ones that most of the times need more attention.
I think 1 BN for each mode, and one final BN from the main mode would be way better. That way you somehow 'incentive' other gamemode sets which isn't bad at all in my opinion. Also you keep the procedure of checking every gamemode properly.
Now the question is how you define the main mode of an hybrid set. The one which has more difficulties? The one which has the hardest difficulty? A mix of last two?
EDIT: Another idea that came to my mind. What if a 'main mode' on hybrid sets is valid when that gamemode has at least 1 extra difficulty or higher (or maybe ~4.8* +)? That way you can have multiple 'main modes'. That would mean that hybrid sets with a lot of harder diffs for each gamemode will need multiple BNs, but I think it's fair enough because those sets are the ones that most of the times need more attention.