So there's a lot of talk of Final Fantasy needing more "mid-core" content. At a base level, I would agree. Problem is...what is "Mid-Core" to everyone? Easy and hard content are easier to design. Make something pants-on-head easy, it's easy for everyone. Make something ball-busting hard, it'll probably be hard for everyone. Mid-core, though? You ask 10 people what that is, and you'd get 10 different answers. What's fairly easy to one person might be fairly hard for another.
So here's my idea. Adjustable difficulty dungeons. Actually remember this being in ye olde Anarchy Online. Wouldn't have to be a free slider like it was in that game, just something that has a 1-10 setting. You give the dungeon a currency, like Criterion. Higher the difficulty, more currency you get. Like 10 for level one, up to 100 for level 10. Maybe have chests in the dungeon that usually give a junk item (firework type item), but a small chance for a cool item (house item, glamour, minions ect ect). Hard difficulty, better odds of getting a cool item.
So what would change with higher difficulty? Well, upping the stats of monsters is, of course, a start. You can also give enemies buffs that adds things to their attacks. For instance, maybe at mid levels, they get a "venomous" buff, that applies a poison debuff to their attacks. Just an example, you could get super crazy with this. Enemies could get more harder to resolve attacks. You could take away telegraphs for some special attacks. Have environmental hazards. Hey, that mountain you're on? Harder difficulties, it becomes a volcano. Now you get to avoid random fireball AoEs. Harder still, now they leave a DoT area for a small time. Harder still, enemies in that area have a buff that allows them to heal if hit with the AoE, or if they're in the DoT area effect. You could put debuffs on the players. This is the stuff just off of my head.
Having this system would allow people to get better at the dungeon (and game) at their own pace. Let's say you think you're pants-on-head bad, so you start at level 1. You get through it, find it's not too bad. So you do 2. Also not bad. You get to 3, and you get some pushback. You play a few times, and you get used to it, and you go to 4. Again, some pushback, but you figure it out. Go to 5. Ok, now it's getting a bit spicy. You do 6, and it's comfortably hard. Not so much that it's annoying, but enough to keep you on your feet. You try 7, and get your teeth kicked in. You keep trying, and maaaybe you eventually get through it, but you decide that 6 is about what you feel comfortable with. Fair enough! You run 6 to get your coins, meaning you get 60 coins per run. That's 50 more then you're getting back on level 1! Encourages people to get better, but still respecting that people do have a maximum cap on how good they can get. Even if your maximum cap IS one, you can still get the stuff, it'll just take you bit longer.
Anyway, it's just an idea, and just a rough one at that.