I remember last year visiting Amsterdam. It has one of the highest theft rates of bikes in the world. Not surprisingly because there are so many bikes. I remember watching one cyclists cycling away towing a specialized bike with his other hand. I couldn't help but think that he was very proficient in doing this. My advise would be to have an emergency emobiliser on the bike so at least nobody could run off with it without your permission.
A bit like a dead man's handle on a train. That would be cool.
When you rent a bike in Amsterdam they give you a bike with a twin lock!
When I am on my V... I stop for 10 to 15 minutes. That bike is somewhat more difficult to cycle away with. Certainly it's impossible to tow and what with the funny shaped pedals and very low Centre of gravity I have some degree of confidence that no one is going to take it.
No respectful yob is going to get up at 8am just to steal a weird looking bike that nobody else has... Right?
If they do... I wouldn't hesitate in buying the latest model. To me it would be a sign of God to upgrade.