I would occasionally benefit from patch in cases when browsing a file whose code is in a package as-of-yet-unloaded, and meta-pointing to a symbol in COMMON-LISP, but that's about all:
I work with the code loaded too but I often work with lots of packages and so am often not in the package that some symbol I want to see is defined. For example, I'm working on function foo and I know that function bar is related to its implementation but bar isn't exported. Right now, I can't type bar and meta-point. I must either navigate to the file in which bar resides myself or type package::bar and meta-point. All the patch does is save me from having to type / remember the package before meta-pointing.
If your patch (I haven't actually tried it, so...) affects arglist lookup it would be a misfeature for me: whenever Slime fails to give me the arglist I expect I know something is wrong.
The patch doesn't alter arglist. It only alters meta-point. A better patch (better in my opinion <smile>) would also alter the behavior of symbol-completion so that I could type "bar meta-tab" and have Lisp find package::bar for me.
How about for a more conservative version: if the symbol isn't found in the current package, prompt user for an alternative package, defaulting to CL-USER?
For my use case, this would be no better than the current behavior of slime... milage may vary, etc.
thanks for the comments,