IMHO, the index file for the app is configurable, and a file named such as main.html can be used if the value for index in angular-cli.json is given.
however, rename index.html file will lead that the app is not available after I upgrade the angular-cli to beta.24. (while working well in beta.18)

OS?

windows 10

Versions.

angular-cli: 1.0.0-beta.24
node: 6.5.0
os: win32 x64
@angular/common: 2.4.1
@angular/compiler: 2.4.1
@angular/compiler-cli: 2.4.1
@angular/core: 2.4.1
@angular/forms: 2.4.1
@angular/http: 2.4.1
@angular/platform-browser: 2.4.1
@angular/platform-browser-dynamic: 2.4.1
@angular/platform-server: 2.4.1
@angular/router: 3.4.1

Repro steps.

1. ng init ( npm install)
2. rename file index.html to main.html
3. change the value of index key to main.html
4. ng serve (build ok)
5. visit the default url (http://localhost:4200)

  "apps": [
    {
      "root": "src",
      "outDir": "dist",
      "assets": [
        "assets",
        "favicon.ico"
      ],
      "index": "main.html",
      "main": "main.ts",
      "test": "test.ts",
      "tsconfig": "tsconfig.json",
      "prefix": "app",
      "mobile": false,
      "styles": [
        "styles.css"
      ],
      "scripts": [],
      "environments": {
        "source": "environments/environment.ts",
        "dev": "environments/environment.ts",
        "prod": "environments/environment.prod.ts"
      }
    }
  ]

The log given by the failure.

page shows "Cannot GET /"
http status code is "404"

Mention any other details that might be useful.

when switch angular-cli to version beta.18, everything goes smoothly.