Without knowing too much about the office stuff, you’re probably on the right track. I believe most office stuff is wrapped up HTML/XML on the backend, so you’d just have to get it into the right format. You may be able to find someone else’s example in some other program to get the right format, but good luck (I didn’t have any).
On the dataflavor/clipboard stuff - yes, you’ll need to implement a custom class in Jython that implements the Java Transferable interface; that’s what will do the actual translation of “thing in Ignition” into “HTML on the clipboard”. I have a (somewhat overkill for your needs) example of implementing the Transferable interface here: PDF report linking