Well, I do secure the whole device with Touch ID. What makes me nervous, though, is if you hand your unlocked iPad to someone you do trust (family member, etc), and they accidentally tap something they shouldn't.
For example, I have some scripts that do somewhat destructive things, like remove production servers from load balancers. I'd rather not have to type my password every time to run the script - but if I store the password in the keychain, then someone borrowing my iPad could do it by accident.
That said - I understand I could probably work around the "accident" case by adding my own Touch ID check in the script, as suggested earlier. But I'd feel better if there was a system-level thing...
Seems like the ideal thing (for me, anyway!) might be to bring back the master password, but be able to use Touch ID instead of that master password.