The one downside, or rather just an added analysis point, of using only OEM CAN components in the build is that I'll have to make sure that everything plays well together. Each component has CAN ID's that it uses for status messages and ones it listens to for commands. The complicated issue here is that these modules were designed for use on different vehicles, and different OEMs all together. If I threw everything on a single CAN bus two modules could use the same ID for status messages, or even worse, a status message from one module could be a command ID for another.
The RX8 cluster is primarily controlled through the CAN bus and listens for other modules broadcasting speed, rpm, temps, error codes, etc. Since the ECU will no longer be on the bus broadcasting these parameters (and there is no ICE engine to get sensor inputs from) I will have to send the appropriate CAN messages myself.