Question

Is there a way to ask to enable access for assistive device in a popup windows (NSAlert like) with a button directly in the popup window?

Answer 1

No, users have to open the System Preferences to enable this.

You can provide a button to navigate to the right System Preference page though:

[[NSWorkspace sharedWorkspace] openFile:@"/System/Library/PreferencePanes/UniversalAccessPref.prefPane"];