I'm currently working on a module that does just that. My current patch got rejected on grounds of changing too much code for a rarely used feature, so we decided on a compromise which is to make it available as a module. The module still needs to be written, but if you require this in the meantime, you can look at my current patch at https://github.com/odoo/odoo/pull/2139 - the final module will use roughly the same logic, but it will dispense with the --debug-server-actions flag and use the already existing --debug flag instead.

I'm afraid there is no easy way to do that. You could copy the python code in a method of the model the server action applies to, and call that method with the right ids and context.