One thing we've noticed that has come up over the years is that sometimes you just need to move assets to other layouts--which can be tricky as there isn't a way to do it within the UI.
In needing to do this, we've come up with a fairly easy solution. The flow works like this:
Select source/destination for assets
A template is generated for you to fill out what to place where
Once template is filled out, it's smooth sailing from there
It might not be perfect yet, but we've moved a few hundred thousand assets between layouts with it already for customers and test accounts.
Feel free to check this link to make sure you always have the latest and greatest version of the script (I've also attached a copy of the script to this post). It's been included in our fork of ITGlue Migration Script since post-ITGlue Migrations are the most common time we need to move Assets around.
It's fairly easy to use and we will continue to improve upon it, so any ideas or recommendations are welcome.
For more-specific details and instructions, you can check the dedicated readme, here.