I'm sorry if this has been covered...its a worthy topic that id like to add 2 cents but with nearly 100 pages already...im going to be a gomer and blurt out something that has probably already been covered.
I have no thoughts on maximizing revenue through auto-renew or how to get new members in here. The only area I can speak on is the attractiveness of participation to new members.
At one point, I joined and just enjoyed playing the games and didn't think much about ranking. Playing risk is fun! And hey...there are hundreds of other maps too! Cool! Hey look speed games, that seems fun - time to throw some money down.
Then something changed, I got hooked on the ranking system, and the idea of being a Sargent seemed pretty sweet. I spent some effort playing a few maps over and over. I devised a few basic strategies. I joined some games with some senior players thinking that sometimes the dice roll the right way and beating a bunch of high ranking officers would be a great way to level up quickly. Sometimes it worked. Often it didnt, and I made rookie mistakes that drew a lot of players ire. I met a lot of rude people scolding me for poor play. Some people on this site...need to go for more walks.
It is hard to gain new ground here on CC as a newb. There has been nearly 10 years of people sharpening their skills and learning all the complex strategies of the maps and all of their strategic variations. I am currently a major and there are 1000 players here with a higher score. There are only 8000 members here, and a large % of them are high ranking officers! Even a couple of years ago I was at this score in something like 700th place out of 12000 members.
Some CC'ers can take a lesson from poker players: be nice to people who play badly. You will beat them eventually, you cant get upset that a bad player gets lucky and wins in the odd game. Good poker players and casinos try to make the game inviting to greenhorn players. I don't think you have to change anything for the people who like the CC experience, but I wonder if there could be a way to buffer the poor or mildly ambivalent players that could make up a lot of potential membership numbers. Rookie games where only sargents and under can join?
I think a lot of casual players would enjoy the speed games. The speed games are unfortunately the place where peoples behavior is at its worst - Fire-breathing from even very experienced players. Vitriol really comes through clear over the internet, and some people are just here to have a bit of fun.
As long as they don't look,we can rip them off.. 
CAN YOU FEEL THE LOVE OF BEING GOLD? FEEL THE LOVE.. 
..I don't know why they got ride of Classic Art and Classic Shapes...They should bring them back..to go along with CLASSIC... We have 3 Age of Realms that are just about the same. 9 USA maps...WWII Eastern Front..WWII Western Front...WWII Europe...2 Slovakia maps again...2 Europe maps....A bunch of others that are just about the same....Who knows why Art and Shapes were AXED..Maybe to keep things under 100 maps...Before the MAP explosion..Where maps were coming out . All over the place...Some people just want to roll the dice and get to fighting. Not try and read a novel of directions. (If the MOON is in alignment with Jupiter and a dog is peeing east on a Mexican beach..you get +5 armies. But if a zebra is swimming across the English Channel with a monkey on it's back..you get -3 armies)..I'm mean COME ON PEOPLE...STOP ALREADY. 
Might need to vault some settings as well.