Hey there!
I would like to hide the Assign and the Assign to me button without losing their functionality. Let me explain...
We have a custom field (Owner). The Owner of a ticket is the person who is in charge of resolving an issue. The assignee of an issue (if owner != assignee) is the person who should answer a question that occured during reading / analysing the issue.
We configured a workflow for that (Request Information). The workflow works like this: The user presses the Request Information button, decides on the assignee and asks the assignee a question.
The assignee should answer this question via the workflow button (Provide Information) - not with the assign button. The Workflow then copies the Owner value to the assignee value.
Anyway, if the assignee is not the correct contact person, it should be possible to pass on an request to the correct contact person. Therefore, we use: Pass On Request (also custom workflow) where the user can choose the assignee.
I read about the workflow properties: https://answers.atlassian.com/questions/44943/can-i-remove-the-assign-and-assign-to-me-options-from-tickets-in-specific-statuses but these don't work well for my use case. They only work for the 'Provide Information' usecase, but not for the pass on request. The 'Provide Information' usecase copies the owner to the assignee field, so there is no direct assignment.
When using the properties for the 'Pass On Request' the user should be able to assign the issue to another user, but only via the 'Pass On Request' button, not the Assign / Assign to Me button. When i use the property jira.permission.assign.$group the assign button is hidden, but i can also not assign via the custom workflow button 
Hence, I would like to know if there is any possibility to only hide those button, but not remove the functionality of the assign process.