Can't be bothered to quote people at this point, but before 100, you can easily level in 0+ equips, and I fully agree it's not hard, just takes time and effort (which a newer, not as invested player probably won't have).
However, this does not mean that tower is currently 'too easy'. At this point in the game, there's a problem with no one else running the tower, so people are forced to solo. Granted, you could grab one or two others if you are in an active academy, but you need to also cater to people who are forced to solo.
I suggest instead of 'increasing difficulty by 20%' - (and I do note that tower is relatively easy for newbies, especially if they did the questline, which they would have if they're in the tower, and especially if they took the time to get that free armor from questline) - to remove the buff that has been added to the tower which increases a players def and damage. It was hard before that buff, but on certain classes, you could still solo back then, although certainly, not all classes could in 0+ gear.
Overall, I would say it is a good idea, Lucy, and thank you for bringing it up, but you need to be aware that like everything else, there are pro and cons to any idea. No one is trying to attack you for your idea, they're just voicing their doubts. I too, have fond memories of Tower of Iyzel, it was actually where I met my first friends in Fiesta. But as a veteran player, I am quite aware that a lot of people would rather go for the 'best EXP' option. The reason I even mention this is because every new player I see asks where to go/what to do next and I always see someone giving the best leveling options instead of anything else. Newbies will ask because they also want to hit 'good content' quickly, and veterans are the ones giving these ("bad") answers.
Perhaps having a Hard Core mode on those lower level dungeons would be what you are looking for.
I like the idea of having chests in all dungeons, most do not have this (I would not include LN's single egg as a chest).
One more thing, when tower was first released, it did literally give you a level per turn in - and this was nerfed shortly after, which was what Aerro was referring to. It seemed you didn't understand that was her concern. As of now, I would still just hoard those tower quests
I don't think speed leveling is a non-option anymore as quests at that level is just so fast now, we don't need to save tower quests or visit even the 30-40 leveling hotspot in DP2. Quests alone will do the job. Perhaps we should think of nerfing those pre 60 quests too