As already suggested, I think http://geck.gamesas.com/index.php/DisablePlayerControls is your best bet. Specifically:
DisablePlayerControls 0 0 0 1
...and then at some point:
EnablePlayerControls 0 0 0 1
...so POV switching works as usual again. I'm not sure if you'd have to wait until the whole knockdown sequence was complete to enable POV switching again - you might be able to have the EnablePlayerControls line immediately after DisablePlayerControls, which would be nice - unless you don't even want to allow the player to manually toggle POV during that time.
By the way shadeMe,
toggleFirstPerson is an OBSE function - we don't have anything equivalent for FO3.