We have the following situation:
A webmaster offers automatic account upgrades. When a member in the forum reaches 50 posts he'll be able to create new threads. When he gets 5 likes he'll be able to like other members' posts.
In General: When a member in the group x reaches x of x he'll be granted access to x.
The traditional way of doing this is to copy the current user-group and grant the newly created group the permission of x (liking and/or posting threads, etc).. This way is difficult to implement and it becomes very difficult to control when many permissions need to be granted for many groups.
My suggestion is the following: To include an account permission upgrade option in the account upgrades section in the control panel to allow administrators to grant specific permissions (from the list) when the user in a specific user-group achieve specific thing.
For example, I click "Add Permission upgrade" from the control panel, I chose the user-group, I set the condition (the goal that a member have to achieve) and chose the permission which will be granted when the condition is fulfilled.
Like this post if you want this to be implemented in xenForo.