• Use black paper for all seals (anti-Byakugan measure).
• After filling Implosion Seals with air, put them on top of each other and roll them up tightly.
• Put the SIN roll into a compact (5x5x30 cm? depends on seals' size) but sturdy metal box encased in waterproof leather. Attach LBFs hooked up to explosion seals inside the box, such that any structural damage to it (or an attempt to disassemble it) results in detonation.
• Incorporate a spring-based 30-hour timer and a combination lock into the box's lid.
-----• Correctly inputting the password gives access to the insides, allowing to reset the timer, carefully remove the SINs, or conduct maintenance.
-----• If the timer isn't reset, the mechanism waves a bar between LBFs, activating them.
• Possible improvements:
-----• Can anti-Byakugan seals be moved while active? If yes, put a small-radius one inside the device — no need for black paper.
----------• If they can't be, only ever input the password under (stationary) anti-Byakugan seals.
-----• Replace the combination lock with a locking seal that responds only to the correct chakra signature (or which needs to be unlocked by some highly specific chakra manipulation, one resistant to reverse-engineering
and difficult to learn (anti-Yamanaka measure)). We already
have an example of a chakra-discriminating locking seal.
-----• Replace the timer with a seal-based one.
-----• Ideally, combine most of the support seals into one: a seal which, if it isn't reset by a specific
complex chakra-based interaction every 24 hours, explodes.
• Tech tree:
-----• Version 0: Bare-bones prototype. No lock, no timer, no internal LBFs, only the sturdy box and anti-Byakugan seals (if movable). Manual activation.
-----• Version 1: Add the combination lock, the timer, and internal LBFs with explosives. Use a seal-based timer if possible.
-----• Version 2: Combine the lock, the timer, and the explosives into a single seal.