"...premium currency can only be gained by controlling 'gyms'; only the most powerful can reliably control gyms; the most powerful thus have the most disposable premium currency, leading to a self-reinforcing loop."
Boy was I spot-on! There are ten Pokemon Go gyms within reasonable walking distance to my house. All ten of them have looked just like this for about three weeks now (all ten Pokemon between 2000 and 3500 CP):
If you flip through the Pokemon on these gyms, only about fifteen discrete players are represented. No one else-- not even other blue team people-- can utilize the gym mechanic in the game at all, henceforth; these fifteen people permanently "won" the gym mechanic, totally removing that aspect of the game from everyone else, via exactly what I said in my review!
This would be super easy to fix by simply taking inspiration from the free market; why not alter the gyms so that, once per day, anyone can swipe them-- sort of like a Pokestop-- and get a little premium currency? The more powerful the gym, the more currency it gives out. The wealthier the fifteen or so gym controllers get, the more they enrich everyone else in the process.
To make it even more free market-like, perhaps there could also be competition between gyms for business? Maybe the gyms only level up by getting swiped by non-owners, and the only way to attract non-owners is by offering items? A small group of upstart players could create a "disruptive" new gym by offering attractive item packages-- maybe even actual Pokemon?-- rebooting things just like what happens in real life (anyone remember IBM?).