I live in a regional city and despite having 75 gyms within 10 minutes drive of each other, there is a lot of contention on the gyms meaning you have to take many to get your coins for the day.
I think it would be good to remove the current limit of 6 players to a gym, but this would come at a cost.
Option 1:
The more pokemon in the gym, the faster their cp drops, the less effective berries are at healing and golden razz usage would become more limited, e.g. 10 monsters in gym might mean players can only feed 5 gold razz per monster instead of 10, 20 limits to 3, you get the drift.
Option 2:
Cp Cap, by this a gym might be limited to say 20,000cp total, pokemons cp would decay same as it does atm, but other team members can come along and add monsters if the total cp has dropped, but pokemon to be added can’t make the total cp exceed the limit, e.g. total cp of 18,000 means a player can add a pokemon of up to 2,000cp.