I am thinking on the Mane 6 & Twilight’s counterparts VS Ponyscopes:
 
-Twilight Sparkle VS Gemini Twins.  
-Sunset Shimmer VS Aries & Capricorn.  
-Starlight Glimmer VS Scorpio & Acuarius.  
-Trixie VS Cancer & Pisces.  
-Rarity VS Virgo.  
-Rainbow Dash VS Sagittarius.  
-Fluttershy VS Libra.  
-Applejack VS Taurus.  
-Pinkie Pie VS Leo.

@Epicalaxy Master  
Same.

Great idea, but I don’t wanna hurt them…

Cancer  
Note: (This thing used to be powerful enough to kill players 3 times its level)

Also, Aquarius is the weird dream sequence level….

Well, first off…. Do we each start with our matching zodiacs, and continue on specific paths from there, or do we fight them in the same order as they appear in the chart?

Cancer is a giant enemy crab

That’s easy.
 
Taurus  
Gemini 1 & Gemini 2  
Cancer  
Leo  
Virgo (Fights more like an Aquarius.)  
Libra  
Capricorn  
Bonus Post-Game Boss: Ophiuchus
 
That should save you half the time and with bonus crossover bait.

With Gemini, you have to trick the one into hitting the other. Obviously.

@Background Pony  
Or more like fighting Koume and Kotake.

I imagine fighting Gemini would be like fighting Master Hand & Crazy Hand, able to fight on their own but can do deadly combo attacks together

Aquarius would have to be a time limit fight. The more time ticks down fighting her, the more flooded the room gets. When it reaches zero, the room is filled with water, resulting in an instant death.
 
Gemini, Libra & Sagittarius would be strategic and quick thinking such as reflecting the proper spell one twin cast onto the other, finding the right amount of stuff to put onto a scale to reach her, and dodging arrows while in a run to him.
 
Aries, Cancer, Leo, Pisces, Scorpio & Taurus would be either a mob survival fight or a monstrous one-on-one fight due to the fact they also represent animals, fish and arachnids.
 
Virgo would be the second-to-last last boss you face, able to mimic some of the attack patterns of her fellow zodiacs until her health is half. Round 2(Incase you lost any allies) she summons your brainwashed fallen allies to fight you until her health’s depleted. Round 3 she goes all out with her unique style and her health is fully restored along with yours. If she’s going to defeat you, she rather do it when you’re at full health and not like a coward.

I get the feeling Libra would have some fierce rubberband AI.

what if they’re just incarnations of constellations like the ursas were?

Leo would roar exactly like a lion, stunning your character with surprise so she could line up a pounce.

Like megaman.

Depending on how they’d do it, sign me UP.

They don’t have to be mind controlled, the concept of friendly bosses isn’t too rare in video games. Like many bosses in Touhou, or like Pokémon Gym Leaders.

Eh. The gimmick wouldn’t be that you defeat them yourself, but rather you have to be clever and manipulate them to defeat each other. Has there already been a game like that?

Pisces would be a boss where she would ride one of two enormous fish that do most of the attacking for her. Either Pisces herself will be the boss’s weakpoint, or you have to K.O. her two fish before you can get to Pisces.

ok What?

@Prince Leaf  
On second thought, your idea would be AWESOME in a Megaman clone. If you beat Pisces, Aquarius becomes the Final Boss. If you don’t, Aquarius is just a warm-up.

@Prince Leaf  
That would be some awesome No More Heroes-level mindfuckery. Still think this sort of game would tend towards Megaman-style rock-paper-scissors gameplay.

If those “things” are true,we are kinda fucked.

@Morfean  
Nah. The way I see it, Aquarius would come across as borderline unbeatable and just when you’re about to be annihilated, Pisces comes over and knocks Aquarius out for stealing her fish. You would then escape in the confusion.