Ok lets solve this as simply as possible otherwise or these rules will explode my head soon.
Restricted races can have maximum fields (15 a side, or as long as there even) depending on numbers.
This will make sure everyone has at least multiple horses competing in the cup.
These races will not have to be selected by the captains, just nominated normaly. However if the field is uneven , say 10 from The Rest and 11 from Europe) Padraig will choose a runner to remove.

To be eligable for the restricted races it will be as normal (number of wins in the leauge).

Restricted trainers should be carefull when entering in the open races as there horse may not be picked where the better option would be to enter your horse in the resricted race where you pretty much guarenteed a start.

These are just my views are are open to debate.
Hope they make sense, its friggin hot outside and I can't concentrate.
Off for an icypole.

Cheers Tim.