The reason these features are not available because Site.pro on our hosting is using a free, promotional tier. Enabling access to the advanced features (as well as removing the page limit) would require us to pay for a premium Site.pro license, and the cost per site are just too high for free hosting.
If you like Site.pro and wait the full functionality of their web builder, you can get a paid plan at Site.pro directly that includes both premium website hosting as well as the full builder functionality.