Fennel
1 - if you can’t reverse you shouldn’t be driving.
2 - if he takes you up on it and decides to reverse, then smashes your car, your insurance won’t cover it, as he’s not on your policy and, at best, he’s only third party with his own insurance.
What you have decided to be a very smart remark could be a very expensive mistake.
Also, the fact that you stated you couldn’t reverse, would almost certainly mean you losing your licence in the event of any incident.
Not to mention that even if nothing happened, if anyone did this to me, I would take their details and my next stop would be at police station to report that driver of this car is not capable of driving, again almost certainly loss of licence.
So please, instead of thinking this is a very cleverly retort, practice your reversing.