Port-A-Brig improvements.

[Sundance]

If the portabrig is used in a smart way there is currently no chance of escape, other than the extraordinary (implants, other bad guy powers) or being given enough time to uncuff. 

These two scenarios happen far more frequently than you are giving it credit for. Also, having a backup sec pda is another example. This window of opportunity is vital so that the port-a-brig serves the purpose instead of being a port-a-solitary.

In short:
Autoejection: Sure! Sounds fun and doesn't seem like it would fuck over the prisoner, unless you somehow manage to rig it so the port-a-brig is teleported into a drone nest.
Autostun: No. As outlined above.
Autolock: Already a feature. Check the sec pda
Autoclothe: Not a bad idea, but a bit much for a port-a-brig. Would be quite suitable as a static object in security, near the brig, which swaps instead of strips.