You may want to just rebuild the controller to v8 instead.
I am currently working on something similar.
A key factor is just how many GRE tunnels are being terminated, because one of the major changes from v6 to v8 is the database moving to a completely different platform (NoSQL to PostgreSQL or something like that). The migration tool handles the migration of the database, so it is a good option if you have a large number of whitelisted APs.
I really wish the migration tool offered just a db migration tool, but unfortunately it is all-or-nothing.
If rebuilding to v8 you would need physical access to the controller as you will need to run the initial setup wizard again.
The migration tool requires you to temporarily set up a VMware-only VM image in your network. This might be a consideration factor if your org only uses Hyper-V, or if you don't have spare VM resources, or if due to security and bureaucracy setting up a temp VM is a hassle.
In your place if I had easy physical access to the 7010 and a small whitelist db, I would just rebuild it and thus completely avoid any potential issues caused by the migration tool.