Here's a feature I'm looking for. I'm working on building such a tool using a Raspberry Pi, but believe this might be an easy firmware update to a Picoscope, especially for the new 2000 series.
In my work, I'd like a CAN bus data RECORDER and PLAYER. I'd like to be able to attach to a CAN bus in a vehicle and then, record all CAN bus commands for various session lengths, and then be able to play it back into the CAN bus for simulation and testing, either in the vehicle, or attached to components on a bench. Adding features to be able to pick specific start, stop, and loop points would also be desirable. And ability to flag or highlight specific identifiers or entire CAN messages (by color perhaps) would also be of interest.
You can do what you are talking about using an Arduino and a CAN Bus Shield. The hardware is really the easy bit. All the work is in decoding the Parameter ID's, decoding the Data and working how each manufacturer is using the Communication Standard. There's loads of good info. on the Arduino Forum. Some good beginner stuff on Instructables.com and there's a good video on you tube on Car Hacking at DEFCON, that will give you a good idea of the sort of work involved in what you're looking at trying to do.