element-sugar.html

<import src="jquery" as="$">
<import src="squid.html" element-as="my-squid">

<my-squid></my-squid>

mostly-es6.html

<script type="module">
import Squid from 'squid.html'
document.registerElement('my-squid', Squid)
</script>
<my-squid></my-squid>

squid.html

<import src="tentacle.html" element-as="x-tentacle">
<import src="ink.html" element-as="x-ink">

<template>
  <x-template></x-template>
  <x-ink></x-ink>
</template>
<script type="module">
export default class Squid extends HTMLElement {
  // ...
}
</script>