Speaking from a purely database developer standpoint here...
The biggest issue I see would be conflicting primary ID's. Since database 1 contains a lot of info, and database 2 would contain a lot of data, most of which would not be the same, but the IDs would be, you'd get conflicting errors.
I'm not sure how SA would handle that, if it didn't crash outright. If you know anything about Access, you could go into the database and manually merge data, this would allow for unique IDs where needed, but would be a time consuming process.