When you break a lucky block, most of the time you just get an item. Even when something spawns you can just run away from it or kill it easily, there are very few threats from the lucky blocks themselves. I'm suggesting more bad things happen, such as:
- More hostile mobs
- Traps like cages or pressure plates with TNT
- Things like random teleports or inventory shuffling that are slightly annoying
- Things like TNT or arrow or anvil rain
These changes would make lucky blocks more "random" as right now they mainly give good things, and would make breaking a lucky block more suspenseful as you do not know if you will get something good or bad.
The rainbow lucky block in the center should also have a chance to do something bad, such as a massive explosion or an army of mobs.