x.ts

class SharedStore {
  hydrate(ctx) {
    this.data = ctx.data
  }
}

const $sharedStore = new SharedStore()

class FeatureStore {
  data = $sharedStore.data

  hydrate(ctx) {
    $sharedStore.hydrate(ctx)
  }
}

Instead this approach we can use separate store into view:

function Feature() {
  const sharedStore = useStore($sharedStore)
  const featureStore = useStore($FeatureStore)
}

Because I guess derived store is not better solution.