I was preparing this idea for an update of my Exploration Revamp suggestion, but seeing as this topic is right here, I may as well just use it.
So the idea is for bosses. Most single monster bosses are fairly easy to beat. Even if, hypothetically, they were immune to insta-ko moves, lethal damage moves, and all status effects, they can still be taken down by using Purpie and/or Moku. And if you make them immune to that, then there are plenty of other cheese strategies for players to use. My point is, Neo is too complicated, and too severely powercrept, for bosses that just have a lot of health to be a threat. So, the idea is to divide the boss battle into phases which each need to be fought individually.
The basic idea is pretty simple. The boss’s health bar is divided into any number of phases. No matter how much damage you deal, you will never go further than one phase, so if the boss’s current phase has 1 health left, and you deal 10,000 damage, the boss will only take 1 damage, enough to move on to the next phase, Each time you deal enough damage to move on to the next phase, the boss will use a special attack. This attack could be any number of things. It could gain stealth, it could stun a random target, it could deal lethal damage to all of your monsters, ignoring Hold Ground and Shield. Whatever the case, this would be a dangerous attack that could change the tide of battle. It will also gain new moves, and may change its pattern of attack. On top of that, the boss will sometimes cast a field effect, which effects all monsters in some way.
Let’s take an example of a stun based boss with three phases. It starts in phase one, with two moves, Stun Flash Unlimited, and Ultrathunder. In this phase, it is fairly weak, and you can easily deal enough damage to get to phase 2. Upon entering phase 2, it uses a special attack that stuns all of your monsters for 200 seconds, casts a field effect that makes it so that stun absorbers and stun counters no longer work, and gains the passive ability Soul Bearer, and the active ability Timestrike. With this new moveset, it is significantly more challenging to defeat. However, you eventually manage it, and you are greeted by the third phase. In this phase, the boss uses a special attack that kills all monsters with anti-stun moves, casts a field effect that makes anti-stun moves no longer work, and gains the passive abilities Ion Field and Time Freeze and the active ability Faststrike, and all of its moves cost less TU. In this phase, the boss is even harder, and the battle that once seemed easy is now a back-and-forth struggle.
As you can see from this example, the boss gets progressively harder as time goes on, and new field effects make it harder and harder to hard-counter the boss’s niche. More difficult bosses with higher ratings could have 5-10 different phases, quickly becoming near impossible to beat unless you specifically planned for them(made possible by the information tab). All bosses would also be immune to all status effects, lethal moves, OHKO moves, and attacks like Delta Super Beam or Mojimojiha, just to force players to actually plan.