but as i said. it was just an idea after all

This is one of the benefits from a 3d light program i use a lot called "capture" sweden. if u need to replace a fixture with another u just simply drag and drop it from the library onto the old fixtures.

I imagine it transfers standardized information like the dimmer, channel, circuit, gel color, etc from the old fixture to the new one; this is easy because those properties are universal.

To visualize why this wouldn't work in Isadora, you have to understand that not all these properties in Isadora are standard across actors. It'd be like having an ETC Source 4 ERS with an iris, gobo, and color scroller and then you replace that fixture with a Par64. How would the software transfer those properties to a lighting instrument that doesn't support those attachments? In short, it can't. 

If it tried, there would be all sorts of differences that we couldn't anticipate. Also would we maintain a list of what actors are allowed to replace which actors? How would we indicate to the users which actors are viable replacements for which actors? It would likely become a UI and UX kerfuffle. All in all, it seems to me that updating a legacy patch to the most recent version of the software is more easily dealt with by just manually replacing actors instead of trying to create an inevitably error-prone automated solution for a very delicate and intricate process.

The new actors often don't have the same inputs as the old ones.

 It's not possible precisely for this reason.

That being said, Cmd+3 and Cmd+4 allow you to grab multiple links going to the same input/output, which makes re-patching much faster.

http://g.recordit.co/v7Yn4G5BzY.gif