Gambling! Make this a casino! Let us gamble for EC, Dil, and GPL different games for each, let us chose the conversion when placing bets. EC for GPL, GPL for Dilithium, etc. put a console that can access these forums.
thats just a couple. make all this exclusive to the Captains table and only for gold membership.
Access to the Captain's Table is by Lifetime Subscription or getting the 400 day Veteran Reward. So it's already a defacto gold membership "feature"