Porta Fractis looks cool and fluffy. But I think it will be useless in the end:
>Force a Rhino to disembark
The player disembarks the marines behind it. Now you're forced to attack an empty Rhino - useless
>Force a Land Raider to disembark
Now you have to deal with a Land Raider *and* Terminators (unseal the portal is range 6").