Miserablise selected outbound URLS?

[Jah-Hools]

Over the last 10 years my forum has been solidly 'gamed' by several people and while I dont want to delete their content I would love to discretely, 'miserable-ize" the outbound URLS they have seeded my forum with

make them slower than other urls
take people to blank pages sometimes
Work fine other times

But not so that it can really be 'figured out' by them..

Or is there a better idea..

Any ideas?

Thanks