Can you have deferred services with emberjs?

I am trying to load data using Ember CLI from a legacy API that seems to be unsuited to using Ember Data. This data will typically be loaded when the page loads and then reused in many places throughout the app. I have created a service 'legacy_data' for this:

import Ember from 'ember';

export default Ember.Service.extend({
  ready: null,
  legacy_data: null,

  init(){
   this.ready = Ember.$.ajax( ... ).done(function(legacy_data){
     this.set('legacy_data', legacy_data);
  }

  computed_attr: Ember.computed('legacy_data', function(){ ... },

  ...more functions and computed attributes
});

Because 'init' function does not seem to support returning a promise (Like the model hook on a route does), whenever I want to use this service, I have to do something like this:

injected_service.ready.then(function(legacy_data){
 ... use service
});

Which in practice means I end up with a whole bunch of additional promise handling in my codebase - It feels like I am swimming against the current on this one.

Is there a better way of doing this? Perhaps a lifecycle hook or a factory/initializer that supports deferred service initialization, so that I do not then have to worry about it everywhere else in my codebase? Do initializers support this? I have not seen it in any examples of it. Is there an alternative way of working around this issue? (Ember data must handle this same issue somehow, but I am new to the framework so am unsure)

Thank you for your help.