inner.html

<div>hola</div>

inner.js

define(['widget', 'template!inner.html'], function (Widget, template) {

   return Widget.extend({
       'sig/initialize': function (signal, deferred) {
           this.html(template, deferred);
       }
   });
});

outer.html

<div data-weave="inner.js"></div>

outer.js

define(['widget', 'template!outer.html'], function (Widget, template) {

   return Widget.extend({
       'sig/initialize': function (signal, deferred) {
           this.html(template, deferred);
       }
   });
});