Revamp Expeditionary Force to be a plausible platform of leveling.
Make it so each Region has an encampment or fortress where NPCs have to defend against encroaching Beastmen. For example, the "Kuzotz" Region should have a fortress in "Eastern Altepa Desert", and the battles there would be recommended for players of level 30-35.
Every other Earth hour a battle would ensue, and it would last one Earth hour as well. The NPC soldiers or guards would be able to hold the fortress on their own regardless of player intervention, but should a player sign up to participate in the fight they'll be able to gain generous amounts of experience points, gil, basic gear, and influence for their home nation upon completion of battle.
Players of any nation may join this Expeditionary Force, but if 5 players from Bastok joined and 4 players from Windurst joined, at the end Bastok would receive slightly more influence in the region than Windurst. Owning a Region would have better benefits too, like free Outpost warps or free Chocobo rides for players from that nation.
This would also be a good opportunity to teach advanced combat tactics in a "live combat situation". For example, have a scripted event where a large group of Beastmen spawn in, then having an NPC Guard yelling, "10 of them all at once?! Hurry, Sleep them immediately!" and having an NPC actually cast Sleepga on the monsters.
This should be something players can join in at any time, even if they're the only person there (hence why NPC Guards/Soldiers need to be able to hold their own). And there should be an Expeditionary Force for each "tier" of levels, example 10-15, 16-20, 46-50, etc
In the one hour down time, players could ask to party up with others who just finished Expeditionary Force, and together they can "grind" for experience points around that area.