AngularJS - Improve page load speed by displaying cached result whilst the page loads

Question

I'm using rendertron to generate pre rendered versions of my pages which are being returned to crawlers and is working well, but my page load speed is very slow for users which is hurting SEO. I'm thinking maybe there is a way to return and display the cached result to the user whilst AngularJS loads the page on the client side. I know buttons which do things won't be functional until the page loads properly, but given this will be a second or 2 this shouldn't' be an issue for the user, so I'm thinking of the best way to do this. In JS, can I simply replace the content of index.html with the cached page and then hope AngularJS updates accordingly, or is there a better way to do this?