1 - When a user requests an access for one of the AD source then a form with available OUs should appear.
2 - User needs to select one
3 - The user should be provisioned in that OU
Is it feasible in ISC? If yes, please provide high level Idea
Usually, Provisioning Policy is used in such cases to add account in AD.
E.g. Based on user details like location or department, user is provisioned in specific DN.
If your requirement cannot be done by provisioning policy, try using custom workflow (“Access Request Submitted” trigger by filtering specific source name)
At a high level, you can create an Access Profile or Role for the access from the Microsoft Active Directory source and attach a request form to it. In the form, provide a dropdown field with the list of allowed OUs, so when the user requests the access they can select the required OU. The selected value can then be mapped in the provisioning policy,which will provision the account directly into the chosen OU.