A VM can be used to make something like a platform independend debuggger work, but won't provide an actual solution regarding user debugging experience since it is very hard to make things like assembler code, pointer tricks, or OpenGL access work in it. I.e. programs cannot be debugged the way they are written.

Using the Delphi debugger would be challenging as well:
- Borland copyright, why would they give it away?
- No support for Dwarf debuginfo
- Only works on Win32
- Has never been used outside the Delphi IDE is probably closely integrated with it

What is needed is a multi-platform capable debugger that supports the Pascal language well. As soon as it exists, IDEs can take advantage of it.