I have a solution that no one will like, but it's probably the least insane one in practice.

1. We move from using leap seconds to leap minutes.

2. We move leap minutes to timezone offset, because time zones are already a clusterfuck and you can't make them any worse anyway.

3. One-time adjustment to all timezones to get the system started.

Result: Z timezone is equivalent to TAI. When you want to account for planet-related BS, you apply a timezone offset.

You can definitely criticize this, but with a caveat: if you believe that Unix timestamp doesn't have leap seconds or that timezones only come in 1-hour increments you clearly have no idea how computer time really works and should probably read up on that first.