I'm feeling degree of tension waiting to hear how this pans out. Hoover sounds like a good idea. In similar situations I've also used bits of blutak, kneeded until soft and sticky, and loops of sticky tape (sticky side out) to effect repair/reshaping. (Sellotape for tweeter domes, more heavy duty stuff for bigger drivers.) Start gently, minimum necessary force etc., whatever you do...
Reminds me of a pair of Meadowlarks I once saw in a shop in Tottenham Court Road with a significant number of cones dinted. Couldn't believe they still had them for sale and were taking such a cavalier attitude to the damage.
Anyway best of luck and please let us know how it goes.