I'm no Test Pilot ( cue for someone who is ) but I'd guess diving with airbrakes already deployed is generally OK - depending on the mechanical setup - but reaching warp 9 in a dive then expecting to deploy the brakes might be asking a bit much, and there's the risk of asymmetric opening or failure which would be a bad thing.
You don't have to be a TP to sort this one out. A set of airbrakes that you couldn't deploy at high speed in order to prevent you exceeding the airframe limit would definitely be in the "Chocolate Fireguard" category. The above applies to a clean configuration, the situation may well be different with flaps/slats deployed
YS