I've been asked to post this as a feature request from a client. 

While I know there is support to create javascript that will make a field read only based on some action, what my customer would like is the ability to not have to do this - they'd love to be able to do more with field rules instead. 

There's two features they'd like like added:

1) "Set Read Only"/ "Unset Read Only"  - the business use case for this is to have a field that was filled in successfully via a lookup function to not be editable. This is something that can be done via javascript but this is rather intimidating for some users that may be creating forms for their departments. 

2) "Set Required"/"Unset Required" - the business use case is pretty much the same. If field X is filled in, require Z as well. Again, they love the fact that they can empower power users to create their own forms, they just don't want them trying to debug javascript for what they feel are simple extensions.