I've been thinking about how mist energy could be improved, and I believe I've come to two plausible ideas on what could be done. I feel that mist energy should enable players to do a fair amount more than it does currently; it's limited to crafting 2* items, and on mist alone you can't afford to even die once in a T3 run.

So, the idea is to allow players to pay energy to expand either their mist capacity or mist regeneration rate. The idea is to allow free players to (with a lot of time invested) to either craft items of higher ranks purely on mist energy or be able to play more during a single day. It may also allow paying customers to invest a bulk amount of money to allow them to play more later, and in that line push non-paying customers over the edge to buy energy to speed up the process. I've thought of three ways this might be feasible

1) Allow players to trade a high amount of energy for a smaller permanent gain to their capacity or regeneration rate; as an example baseline imagine a player could pay 100 energy to extend their mist capacity by 10, or regenerate 110 energy in the time it currently takes to get 100. The cost for this could scale, so the price might go up by the same amount (expend a full mist tank to get 10 more capacity/equivalent upgrade to regen) or it might make jumps at key points (200 energy per 10 after 200, 400 energy per 10 after 400)

2) Timed mist tank upgrades in the same style as slot and heat upgrades. 100 energy buys a tank with +100 energy/+100% regen, 200 buys a tank with +300 energy/regen, 400 buys a tank with +700 energy/regen. Capacity and Regeneration upgrades could be sold seperately. It may be necessary to place a limit on how often these can be bought to stop players from never buying energy elsewhere, though.

3) Perhaps more controversial, and would only work for paying customers: offer mist upgrades alongside the energy players purchase. It may make some players jump the fence into becoming paying customers, but players that refuse to pay wouldn't be happy about it not being available to them.

Obviously if OOO chooses to do this, the pricing's up to them. They could even force the payments to be crystal energy only; the important part is that players could eventually become nondependent on the crystal energy market for mere game progression. As a thought of the moment, perhaps OOO could introduce items that can only be bought with crystal energy; as long as players can trade it, that wouldn't prevent free players from accessing premium content.