I realize things like early gear unlocks and progression accelerators are fairly common in the free-to-play market, but games like Path of Exile have also proved that you can make more than sufficient income solely from cosmetics and your community will love you for it as well.

You could even do tiers of cosmetics like EVE Online has, where some are quite cheap and others are very expensive but fancier looking, so people who want to go maximum Special Snowflake will make the jump in order to be more unique compared to other players.

An issue I've frequently seen discussed in free-to-play games is that the player feels like they're slogging through an uphill grind to unlock anything unless they're using every possible progression booster. I think it will be far easier to craft a balanced progression experience and not have anyone put off by feeling like they have to pay to be competitive.