Yes, if you want to be able to re-use your custom page logic then you can make a class that inherits from mojoBasePage, add your custom methods and properties and then inherit from that class in your custom blog pages instead of mojoBasePage.
Note also that you can specify on the StyleSheetCombiner control in layout.master
<portal:StyleSheetCombiner AlwaysShowLeftColumn="true" AlwaysShowRightColumn="true"...
this will make the master page show the side columns even if they have not content system content, but it will affect all pages using the skin.
Hope it helps,