Looks great!
With regards custom sign in page I see 3 ways around.
1. Close your site to guest users in Admin Panel >> Privacy and Permissions >> Global Privacy. This way whenever anybody opens your domain name sign in page will be opened.
You then will need to edit some CSS and .html related to sign in page to make it look more attractive.
Note: you won't be able to show widgets that are currently visible on your main page in your sign in page. Overall your current main page will be accessible only by loged in users.
2. Developing a plugin, which will create a custom page where you can add a sign in form. By placing your new plugin's menu item to the first place in Admin Panel >> Pages and Menus >> Pages and menus>> you will be able to make a sign in page landing one.
Benefit of plugin development is that you won't have to close your site from guest users.
3. Check the Store. I am aware of several plugins for a landing page:
http://www.oxwall.org/store/search/plugin?q=landing
Easiest way is of course #3. Just get a plugin.
The most difficult is #2.
#1 is somewhat in the middle. Doesn't require complex modifications, but you must have basic css and html skills.