Credit card systems have been popular lately and the MEI system is really nice. They are selling retro kits for some Rowe changers (of course they do not sell one for my BC-200) the system just replaces the transporter and nothing else.
The CC system runs around $750 per setup (attaches onto a MEI bill acceptor not included) $165 for the credit card face plate (which is metal not plastic). It is a cellular CC system (which cost $10 a month) and cost 5% for an average ticket less the $10 and 2 3/4% of average above $10.
You could put one CC bill acceptor in you dual changer and then vend tokens. (Like the bi-metal tokens from TokensDirect.) The only problem with the system is that each system needs all the parts and can not share. So if you wanted to install one in every bay then you have to purchase everything over again for each bay. Also $10 a month per system/bay.
I also checked out the Wash Verify CC system which it nice and can be installed in any environment and not even on a meter box. Also you can repair individual pieces on the cc swipe, but the server it Windows XP and uses an Internet connection.