Increase skill/spell learning ability across the board for all races.
Increase exp gained.
Increase bonus to two team ranking.
Remove all non-unique and unessential (i.e. important connecting areas) from the game.
Shuffle area availability. Meaning that at certain times during the game many areas are simply unaccessible. Break it up into four groups or something, and during these times (maybe once a week it reboots and shuffles?) you can only access these areas, which means less areas to hunt.
Remove any uber items; strange bracers, etc, or put some sort of limiter on them that means that too many uber items on you causes the magic/power within them to clash. Meaning you can't have Hunsobo's or similar running around.
Upgrade outfit drastically. There's no reason outfit should not give you at least the basic regear set found on Diku (for fighters anyway). Have it the items increase in power too as you level. Meaning at level 10 you can't kill yourself, hit outfit and have an awesome set, but at 30 you'd get a decent one. Hero might be the equivalent of midnight dragon skin etc.
Reduce preps across the board, reduce Ragers to match.
IMM exp handed out more freely, IMM exp always makes people feel good.
More active global happenings at hero, like easter egg hunts, big bad mofos attacking Galadon, etc.
Make inners more powerful depending on the number of people raiding.
Increase anti-gank code effectiveness.
I dunno, just things off the top of my head, might not all work, or might not all work together, but it would make me start playing again.