So far I'm thinking the best way to approach this project is to follow 3 main paths of progress:  

1. Continue researching/learning. There's a lot about the nitty-gritty side of things that I need to build a better understanding of if I have any hope of getting the FPGA interfaces to work. I'll need to go over communication protocols, power supply and how to implement the data transfer efficiently. (for that I'm thinking DMA)
2. I'll need to go over all the components I've already specced and/or purchase to ensure that they are what I want to go with. As I mentioned before, a lot of these parts have been EoL'd or have an updated version out. Where it makes sense I'll try to stick with what I already own, but if anything stands out I'll have to start planning around the newer option
3. I have to lock down the I/O feature set that I'd like to support. Once I have that, I'll need to build a simulator (I've sold my car since the first round of working on this) in order to debug, test and optimize the various ways I plan on being able to interface with a car. This will also be a good trial run for PCB design as while it'll end up decently complicated, it will be definitely simpler than the PCB used on MagiLog.  

Thoughts, suggestions? If I'm doing something stupid, please save me from myself