I am a fan of breakout boards, bredboards and coloured wires because from time to time I have to build a proof-of concept or I have to connect my idea to an existing device. So I would build a separate pcb and make an I2C connection to control it from the main board.
Of course, when you are enthusiastic for low space you may glue the PRoC module to a free space on the -043 and wire it directly. Only problem will be to arrange the programming of the PRoC module.
I too like using breakout boards... however, since Cypress is promoting this as a viable option (ie, designing it into the board as well as providing information in the user guide) I was hoping it would be fairly easy to drop it on there without the extra effort/cost of the breakout design .. and not sure I can solder that many tiny wires to the module by hand :)
The best would be using a hot-air gun and doing reflow soldering (using solder paste).
Next best thing is probably fixing the module with kapton tape, and then use a fine solder wire to solder the connections. They are on the outside of the module, although just a little bit. This should be enough to get solder on them. If you create shorts, use solder wick to remove them. For a prototype this is OK I think, but I would not do it for a production run.