MCP2200 - which GPIOs for DTR, DCD, DSR and RI?
Perhaps a bit late for your review but have a look at the new Cypress USB to serial bridges. They are apparently able to mimic the footprint of the FT232R and feature the required modem control lines:

http://www.cypress.com/?id=4&amp;rID=83118

and

http://www.cypress.com/?mpn=CY7C65213-28PVXI

We have done some early testing with the controllers and appear to be fine. Based on the Cortex M0 processor but the firmware is not available.