Hm, not sure if that will actually be possible in 3.2 via blueprint settings. While you will be able to set actions per user role, I haven’t seen an example where you could define the roles.
You can prevent creating a user with the admin role though a hook though.
Maybe I could do something like this (don’t know if it’s possible):
In the config file:
if the current user == manager, set a custom panel CSS file and set display:none on the first li tag (Admin in my case) of the user role list displayed in the “Add user” modal …
Yes, that would be an option, but hiding a select option is not really a secure thing to do. The user can just change the value that is sent and there’s no validation in place to prevent that unless you use an additional hook.