The Deathless Shadows: The Uzumaki were feared for a very good reason. The Daimyo of Whirlpool commanded a deathless legion of shadow guards. Tireless, indestructable, powerful and totally loyal, these creations of the sealing arts terrified the other clans and nations. However, no one had seen a shadow guard in over a century, so most thought them to be mere legends. The Legends are awake, and Naruto is their master and heir. Kushina is now a shadow guard and will do anything to protect her lord.
Shadow Guards are a combination of puppetry, metal work, seals, and shadow clones. A chakra-metal and titanium-coltan alloy skeleton with a chakra-metal polyalloy liquid metal sheath allows the puppet to shape-shift into virtually any humanoid form. A shadow clone is sealed into the puppet and powered by chakra gathering and absorbing seals. This allows the clone to use chakra at constant Kage levels for weeks without rest. Chakra from attacks below B rank or without high control is simply absorbed to power the guard. The final step involves summoning the Shinigami to reverse the memory flow of the shadow clone jutsu. When the caster dies, the clone gains the memories of the caster and the technique continues as long as the clone wishes and has chakra from the seals. Other seals enforce loyalty to the Whirlpool Daimyo to prevent rogue guards from becoming threats. After 10 years of service, the clone can disspell if it wishes, but must obey the Daimyo otherwise. The process completes with the puppet "asleep" until the caster dies. Kushina, Mikoto Uchiha and Hitomi Huuyga were a team in the Third Shinobi War. Kushina invited her teamates to become "shadow recruits" after returning from the war and before their marriages. The number of guards can be very large, since every person who did a grand service for Whirlpool, the Daimyo of Whirlpool, or the Uzumaki clan could be invited to become "recruits". The usual reward was to be allow to watch over their loved ones for the first decade, folowed by a decade of service to the clan or Whirlpool. In story terms, this means that Hitomi and Mikoto may not die as they did in cannon, since Kushina is active and would intervene to save her friends.
Note that not all shadow guards chose to be humaniod. Some rare custom shells were made, also for "Zoid-like" machines, Transformers, etc. Mecha will be limited in size to a maximum of 40 meters or so due to the power required to move that much mass. The seals are good, but in general, the larger the body, the less chakra for anything other than movement. This encourages the "big robots with guns" that most mecha anime love. No jutsu for big robots. The "Assaults" as the large guards are called are basically armored transports that inspired Snow Country's chakra armor due to legends about the massive machines ignore attacks.
Assaults move at high Chunin, low Jonin speed on the ground. No tree hopping, or flight. Swimming is also possible for some models, as is walking on the bottom of a moderately deep river or lake. Deep oceans, not so much. The chakra expense of just moving and stay active limits the mecha. Shields and other energy expenditures run off seprate chakra seals that are limited in capacity to a few hours of heavy use at most. Any "signature attacks" are usually powered by the pilot and are thus limited to what the pilot can channel. The Liger's laser claws would count as a B rank attack, and the cutting tail would be A rank, and so on. The rest of the weapons are limited to what puppets normally use: kunai launchers, senbon launchers, poison gas, poisoned weapons, explosive tags, trap jutsu tags and so on. The occasional mecha has chinese rockets from the Mongol period (really big bottle rockets) and mortars.
