If the Preference called #readDocumentAtStartup is set (which it is by 
default), then Squeak should read a file given as an argument like this:

 squeak myBroken.image file:///someDirectory/someFile.st

note that the argument MUST look like an absolute URL!

I just tried this script:

 Smalltalk logError: 'Testing 123' inContext: thisContext to:'Test.log'.

and got a stack trace.

So if you run the above script and don't get a Test.log produced, then you 
aren't even getting to the startup (or the Preference for reading documents 
isn't set).

As far as simulating the Alt-. you can make a script that just does this:

 self halt.

and this will pop up a debugger after interrupting the current process (which 
will be the Morphic process that's starting up the system).