If you already have something pinging your site every 15 minutes that should be keeping the site awake unless the default app pool timeout is less than 15 minutes. If the site is staying awake then startup time shouldn't be a problem. Myself I would not use the AppKeepAlive if you have an external service pingning your site already it is redundant since all the appKeepalive task does is spin up a background thread the pings your home page every 10 minutes.
You can remove skins you are not using and that might reduce compile time a little.
You can delete the /WebStore folder from your site if you are not using the feature and that will remove some files that would be compiled, and then remove WebStore projects from your custom .sln so it doesn't get packaged when you publish. If you previously built it before removing it you would need to also delete it from beneath Web/WebStore in your dev environment because it already got copied there by a post build event, and it wouldn't hurt to also remove the uneeded webstore dlls from the /bin folder