Approach for SharePoint file upload workflow

I'm working on a project that is basically a file upload "wizard" that basically does the following:

1. Entry form to select document library and enter some basic info.
2. Enter additional library-specific information.
3. Tie in some calendar events.

My goals are: - Create this as a sandbox solution using Visual Studio - Avoid hacks and reinventing existing functionality as much as possible.

Some SP features I have run across that might be useful: - Content organizer feature. - Association forms. - Declarative workflows.

Possible approaches I've considered:

1. A content organizer library that kicks off a workflow on submission. Not sure what the user experience for this would be like. Really hoping to keep to a single link -> Next -> Next -> Done kind of approach.
2. A declarative workflow with custom actions containing all the complexity.
3. An association form in front of the built-in document upload form for each library with a follow-on association form for calendar events.

Is this feasible and if so which approach is simplest?

I think I've come to my own conclusions on this. I've decided to go with a Drop Off library as part of the Content Organizer built-in feature (#1 above). This appears to be the simplest approach so far since I can do the majority through configuration in the Entity.xml files of the features. Many of the other methods I tried seems like they would require functionality not available in a Sandbox solution.

In order to achieve this, I defined site columns and added them to custom Document Type, then added this Document Type to all libraries. Using the Drop Off library, I can define rules to move the file based on one of the fields in the custom Document Type. I'm hoping to do any follow-up steps as a workflow that kicks off on the Drop Off library when a file is uploaded or as an Associated Form.