Sounds fun. My favorite starter is Greninja(even if its not the one i picked as a starter in rejuv) so I will use it.
HP:72+10=82
Attack:95+56=151
Defense:67
Sp.Attack:103+55=158
Sp.Defense:71+15=86
Speed:122+40=162
(Defense will stay the same to give it a weakness to physical attacks)
Ability: Ilusion could be a pretty fun ability and I think it fits Greninja because you know stealth, but drizzle works as well here (Honestly Protean is already perfect for Greninja but I will change it anyways)
New Moves: Spectral Thief, Close Combat
I came up with a couple of sets Emergency Sweep Stopper
Greninja @ Focus Sash
Ability: Illusion
EVs: 252 Atk / 252 Spe
Adamant Nature
- Spectral Thief
- Close Combat
- Waterfall
- Ice Punch/Quick Attack
This set is designed to take a hit with sash and steal all their boosts All-Out Physical Attacker
Greninja @ Life Orb/Choice Band/Whatever Z-Crystal you need to muscle through some mons
Ability: Ilusion
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant/Jolly Nature
- Waterfall
- Night Slash/U-Turn
- Gunk Shot
- Close Combat/Rock Slide/Ice Punch All-Out Special Attacker
Greninja @ Life Orb/Choice Specs/Whatever Z-Crystal you need
Ability: Ilusion
EVs: 252 SpA / 4 SpD / 252 Spe
Modest/Timid Nature
- Surf/Hydro Pump
- Dark Pulse
- Ice Beam
- Grass Knot/Extrasensory/Water Shuriken Mixed Attacker
Greninja @ Life Orb/Whatever Z-Crystal you need
Ability: Ilusion
EVs: 80 Atk / 176 SpA / 252 Spe (Just a random spread)
Hasty Nature
- Surf/Hydro Pump
- Dark Pulse/Ice Beam
- Gunk Shot
- Close Combat