Things at the top of my head, implemented in order:
Highly Realistic / Minor Changes to Existing Systems1. Do not show dungeon map to first timers - just like before. (Add trigger points to eventually light up the map, whether partially or all at once)
2. Add a Guild Rank below Veteran that allows that member to have Storage Access. Unranked members NO LONGER HAVE Storage access.
3. Add an option to allow your Island Merchants to Auto-Purchase stuff at a pre-set price. The sellers will decide who to sell to.
Realistic / New Implements1. Better policing / Live GM = no hacks & botters
2. Auction House
3. World Maps
4. Highly Balanced Classes
5. PvP and its variants
6. Turf Wars
7. Patron God System
8. ◇Knowledge (acts like a menu) giving access to News, Armory, Bestiary, Lore, Recordbreakers, Guild Info, etc, etc.
Not Realistic / New Implements1. Turn the Eternity Maze, or add some floors, that's like a Roguelike Dungeon.
2. Hold a bi-annual event during Summer and Christmas where Tilia and the Gang performs in an idol concert, with real voices at least. Doesn't have to be animated. Still shots will do. Those who watch it gets a 48 hour buff.
3. Beggar Class XD
4. Merchant Class
5. Trainer (specializes in Pet Use)
6. Implement Dating Sim Mechanics / P2P Heart System <3
7. Casanova Class (based on Heart System)
8. "Iruna Online OVA" starring Cordal and Specia, chronicling the events before the War.
It's fun to fantasize. ^^