Build automation for Delphi + Oracle
For my Delphi projects, I was using FinalBuilder (itself a Delphi app) way back when. I was always very happy with the product, and it worked very well.
In the meantime, they also launched a Server version of the build tool, so you can set up a full build server and have your code built there.
Another worthy contender back in those days used to be Visual Build - feature by feature the two almost match up, but the "feel" of the app, the ease of use, was with Finalbuilder, in my personal opinion.
I'm not sure if any of the two has direct and specific Oracle support, but at least Finalbuilder can run anything that can be run from the command line, so that should give you plenty of options, really.
I've been using CruiseControl.NET as a Continuous Integration server for our Delphi builds, which integrates quite nicely with NAnt as a build scripting language.
Forgetting about CC.NET, simply using NAnt would provide most/all of what you need, I think.
Combined with the extra NAnt-Contrib library of extra tasks, I have implemented everything you mention with the exception of the Oracle integration. However, you can easily invoke commandline stuff from within NAnt scripts, or write your own NAnt tasks using any .NET language.
NAnt has tasks for integrating with Subversion, or you can simply invoke the svn command line client.
I have invoked BeyondCompare as a diff tool from within my NAnt scripts, used NAnt to send customised HTML emails and execute Installshield builds, along with obviously executing the commmand line Delphi compiler and resource compiler.
NAnt is free and open-source, it's worth checking out.