“Would there ever be a reasonable requirement to make flight 1 or 3 with less than 30 minutes reserves?”
Some aircraft only have around 1 hours fuel but could be landed on a very short strip.
Some aircraft have very limited w & b so by forcing more fuel you would just create another issue of being over weight on takoff.
As I said in my post above, if you have 3 places within 5 min and 10 within 10 min then 30 min reserve is ok, if you are in Scotland with fog then you need a lot more. A machine which can land in 300m is likly to have many more options than a Twin needing 1000m. One rule for all is not the way to go.
Rod1