If you right click on the pose editor icon, there are copy/paste/paste opposite options. It only copies the pose and not keys, but it should get you halfway where you want.
Copy/paste opposite doesn’t currently work with the spine controls, but I can add that to the list of things to add!
You are correct on making modifications to the rig file. If you were to need to rebuild, they would get squashed. How we deal with this at work is wrap all custom modifications into a script and add it to the post script slot when you go to publish your character under the advanced section.
I’ll take a look at the finger control scaling. It seems to be broken for me as well (I swear it used to work!).
as for those locators, in the latest code drop these have been hidden so they do not accidentally get selected. Keying them has unfortunate effects as you’ve found out
