How to scale so that container also grows and takes up space

Question

CSS3 scale transitions work like that. Unfortunately, scaling would overlap other elements as it takes the contents of the container out of the flow by creating a new stacking context (essentially putting all its contents positioned relative to the container) – see the relevant doc description:

If the property has a value different than none, a stacking context
will be created.

Source: MDN

See a demo below scaling all the elements by brute force:

var b, scale = 1, offset, pointers;

window.onload = function() {
  b = document.getElementById("outer");
  offset = b.getBoundingClientRect();
  pointers = Array.prototype.map.call(b.querySelectorAll('.pointer'), function(e) {
    return {
      el: e,
      offset: e.getBoundingClientRect()
    }
  });
}

function increase() {
  scale += 0.1;
  scaleIt();
}

function decrease() {
  scale -= 0.1;
  scaleIt();
}

function scaleIt() {
  b.style.width = scale * offset.width + 'px';
  b.style.height = scale * offset.height + 'px';
  Array.prototype.forEach.call(pointers, function(e) {
    e.el.style.width = scale * e.offset.width + 'px';
    e.el.style.height = scale * e.offset.height + 'px';
    e.el.style.top = scale * e.offset.top + 'px';
    e.el.style.left = scale * e.offset.left + 'px';
  });
}

#outer {
  /*overflow-x: auto;*/
  position: relative;
  transform-origin: left top;
}
.pointer {
  width: 20px;
  height: 20px;
  background-color: orange;
  position: absolute;
}
#outer > img {
  height: 100%;
}

#a1 {
  top: 50px;
  left: 150px;
}
#a2 {
  top: 150px;
  left: 50px;
}
#a3 {
  top: 250px;
  left: 550px;
}

<div>
    <button onclick="increase()">Increase</button>
    <button onclick="decrease()">Decrease</button>
</div>
<div id=outer>
  <img src="http://via.placeholder.com/600x350" />
  <div id="a1" class="pointer">
  </div>
  <div id="a2" class="pointer">
  </div>
  <div id="a3" class="pointer">
  </div>
</div>
<div>
    please don't cover me
</div>

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