I love this idea .
If the event does take place, you get a warning 10 mins before impact (if your ship picks it up)
if you dont choose an action (Attack, Scan or avoid (all based on your points in that ability would be if you succeeded or not)) within the 10 mins, your ship would automaticly attack/avoid (depending on if your attack or defence is higher) but would never scan without your permission.

Attacking would give mineral rewards (failure would be higher damage then usual)
Avoiding would give a slight amount of exp (failure would be a normal hit dependant on level)
Scanning would give artifact or research rewards (very very very rarely an energy cube or somthing of equal value) (failure would be a massive hit to hull (25-50% of max hull?) as you have to lower your shields to scan it)

The quicker you respond the higher your chance.
chance starts off at 100%, after 1 min 98% down to 80% after full time has gone.
then the factor of your chance due to strength against asteroid size and level for overall chance of success.

In my opinion this is the best possible outcome for somthing like this.

No. i don't like the idea to have my hulls degraded by 50%. 20% seems enough since i have over 4k hulls ^^. but i like the other parts of your suggestion!