The Read more functionality is only available in the Blog but you can use jQuery to create a similar effect. I found these plugins with a quick search: Expander, Readmore, Quick and Easy Readmore.
The Child page submenu functionality you asked for is already included in mojoPortal. Some of the included skins do not show a child page submenu because they use a hover and fly-out style menu. What you are asking for can be accomplished with a combination of the DynamicDisplayLevels and StartingNodeOffset settings of the PageMenu control. If you can post the menu hierarchy you are trying to acheive, I can help you come up with something that should work.
As far as skins having features or controls that others do not; for the most part the controls are the same in all of the skins, they are just using different settings to make them behave differently. Also, a lot of things can be done through CSS to make a control look completely different than it was originally intended to look.