Aircraft Carrier Conversion?

During World War Two many civilian ships were converted to Aircraft Carriers. Does anyone think this could be a practical and/or economical way to build a Aircraft Carrier? The market is full of good used merchants many of which could be purchased for pennies! The U.K. had a plan many years a go to convert container ships to Carriers with Harrier in times of conflict and/or war. Just so there are no misunderstanding. I am talking about a Small to Medium VTOL Carrier. No arrest gear and/or catapults.