“What kind of in-game events would you like?”
I would suggest to come up with something like “Randomly generated events”
The first thing that comes to my mind is a Gin tower (like woven echo Nemeses Conquered Tower), but each subsequent level/floor is harder (each new floor introduce new buff for monsters that will added to all previous ones).
For example:
at level 1 the mod: all monsters have +15 to all resistances;
at level 2: all moster have +15 resistances and + have haste;
at level 3: +15 resistances + haste and + 2000 armor;
at level 4: +15 resistances + haste + 2000 armor and monsters deal additionally 10% fire damage.
etc.
And the higher you up - monsters get more significant buffs (both defensive and offensive).
In addition, the higher you climb up tower, more curses will imposed to traveler (maybe every 5 floors). For example:
5th level: 20% less movement speed;
10th level: 20% less movement speed and + 20% less cooldown recovery speed for all skills and spells;
15th level: 20% less movement speed + 20% less cooldown recovery speed for all skills and spells and + all resistances reduced by 10%;
20th level: 20% less movement speed + 20% less cooldown recovery speed for all skills and spells + all resistances reduced by 10% and + 50% less dodge and block chance.
etc.
And the higher you up, more significant curses will be imposed.
Also, there should spawn a random monsters on the floors - sometimes it will be champions, sometimes bosses, sometimes simple and rare monsters etc, so player will not know what awaits him next and it would be more interesting and difficult to climb higher and higher. Also you can add some traps that will randomly appear in random parts of the room, so that it would not be just another grind of monsters. This will help diversify game process from simply grinding mobs and players will need to take care about their moving on map and movement abilities.
All this points together would be quite difficult but at the same time exciting.
Also It could be not a tower, but some kind of Sphinx crypt, where you go down instead of up.
And I think you can invent many similar things, based on such randomly generated mechanics, with their own characteristics, each of which can be responsible for a separate mechanic.
Just come up with something new, your own, don’t copy from others.
P.S.
I really appreciate everything you do, but I don’t want to play PoE 3, I want to play Last Epoch.