So you are looking to transform the birds into endurance athletes. I liked the treadmill option as that allowed for a more natural gate. It would be difficult to setup for sprinting.
I also like the treadmill one better... The wheel one seems stressful... When the rooster tries to stop it keeps rolling him up backwards. Its probably great core exercise for him though.
There are only a few physical qualities that an athlete is required to possess.
Strength
Endurance
Dexterity (agility, balance etc)
Speed
With chickens we could probably add Flight.
For gamefowl we probably need to add Gameness.
If there was a Gamefowl Olympics I would like to see a competition for each of these qualities... or some combination of these qualities. I think events that combines 2 or 3 of these qualities would be better as to prevent specialized breeding... For example a treadmill competition would only test endurance, therefore a breeder would breed specialized running chickens which may or may not possess the other qualities we like to see in gamefowl.