Possible. No reason why it would not be able to be made to work.
How easy it is varies with what is done and it is not always obvious (at least not without considerable programming skills) what that might be.
Back to basics though.
The classic basic cheat is change this area of memory into this other value, possibly doing that every frame but later ones might allow you to do it in response to a button press.
In most simultaneous (as opposed to pass the controller after you die) 2+ player games then each character will probably be its own section of memory with own stats, indeed same generally applies to RPGs as well when you have a party, and even enemies in beat em ups and whatever else.
Your basic cheat is then only going to do the thing that it is aimed at, which in most cases will just be player 1, and possibly triggered by player 1's controller (2,3,4... tend to have their own slots later in memory for consoles, handhelds is a different matter) which may or may not work for you (sometimes you want asymmetrical modes if say 1 player is the dungeon master type role).
Bonus here is as the same data structure is probably replicated however many bytes on for player 2 that you then find this structure by whatever means (if it is something hard to edit like luck in a typical RPG then find something easy like atk in stats and a fixed distance away, in this case for player 2 though) and edit accordingly, or you can just do the basic cheat search routine but with player 2 in mind
https://web.archive.org/web/20080309104350/http://etk.scener.org/?op=tutorial being my general choice of cheat searching guide, it is for the GBA but works much the same whether you are on an Apple II, Wii or raspberry pi.
https://doc.kodewerx.org/index.html covers lists of cheat formats for various consoles though for the Wii then
http://wiigeckocodes.github.io/codetypedocumentation.html looks good). Can be harder to do something like you describe, though actually maybe not as you can probably suck in an enemy, search, fire them out/eat them, search, suck in another, search, fire/eat, search... to get the state that your existing cheat probably twiddles, and then do a conditional code that only does it upon a certain button press/combo.
Major exception in this. While the classic basic cheat is just a memory edit there is the game genie approach to the world which effectively edits the game instead (also why you can patch those in trivially where hardpatching memory stuff does not appear much before the 32 bit era or GBA). Technically this does exist for the Wii but as far as basic cheats are concerned it is noted that a 6x DVD ROM drive is actually rather slow compared to CPU with several hundred megs of memory running in speeds usefully measured in gigahertz. To that end the game's code is usually copied to memory to run and being in memory you get to edit it with cheats.
