The Iceland requirement is almost dull in the rule anyways because Iceland is already under British control if I remember correctly and rarely does Germany go after it.
I want to sit down and create very detail routes for Lend Lease and coming off the top of my head, this is what I can think of.
USA:
A route between Alaska and USSR.
A route between the East Coast to UK.
A route from LA to ANZAC via Sidney that also goes to India to China.
(this is the longest in the game so I am sure if it should be one continues NO or break it up)
UK:
A route from UK to USSR.
A route from UK to France.
A route from UK to India to ANZAC ( I cannot remember if UK directly supplied ANZAC before India or did both with the same fleet)
Some kind of “reserve” Lend Lease to the US from UK, this would be a complex rule to make fair because under history, it involved UK leasing military bases to US.
I can’t remember what else out there but I am sure you can find more. Also, I intentionally ignored non combat Allied Nations that allowed their merchant fleet to move stuff but you can include it because Mexico is already part of the US in 1940.