I was under the impression that Googlebot already executes javascript on pages.
A more interesting idea would be if you do this for every user - prerender the page and send them the result, so they don't have to do the first, heavy js execution themselves. I know it sounds a bit retarded at first - you're basically using javascript as a server-side page renderer, but think about this: You can choose to prerender or not to prerender based on user agent string -- do it for people on mobile phones, but not for desktop users. You can write your entire site with just client-side page generation with javascript and let it run client-side at first, then switch to server-side prerendering once you have better hardware.
Something similar to that, albeit slightly more elegant, is the work that AirBnB has done with their rendr [0] project, which serves prerendered content that's then rerendered with JS if it needs to be changed. You can do similar things with non-Backbone stacks, of course.
A more interesting idea would be if you do this for every user - prerender the page and send them the result, so they don't have to do the first, heavy js execution themselves. I know it sounds a bit retarded at first - you're basically using javascript as a server-side page renderer, but think about this: You can choose to prerender or not to prerender based on user agent string -- do it for people on mobile phones, but not for desktop users. You can write your entire site with just client-side page generation with javascript and let it run client-side at first, then switch to server-side prerendering once you have better hardware.