Hello SamTE,
I started building my own A320 cockpit as well, and am still in study phase. And yes, the FCU is my first goal. Not the easiest panel, but if I can build this, then I convinced myself I can do it.
I'm using FMGS, and was lucky enough to get the API from Jean-Luc. With this, I could build a DLL that fits on the FMGS simulator. I used Sockets (IP) to communicate with a kind of Hardware HUB that connects with my Hardware. This HUB is written in C# (Visual Studio), and connects with my Hardware over USB. The nice thing is that this HUB can be installed on separate PC's, so I can distribute my Hardware. The Hardware itself is based on the PIC-microcontroller. I'm now using the 18F45K50, which doesn't even require a crystal, and still has a stable USB clock. I have written a stack of tools that allows easy control of switches, LED's, 7-segment displays, Rotary Encoders, etc... All software is written by myself.
I now jumped on the hardware. I purchased a Snapmaker 2.0 A350 (CNC, 3D-printer, Laser) and started cutting plexiglass, printed my own Korry-switch and push/pull encoder (these are all pretty expensive to buy, so better make something yourself). I am now experimenting with my laser-engraver to cut out the characters and symbols. This works already great with painted blank plexiglass, but this weekend I'll do a test with the opaque version (better diffusion for backlighting). All this requires a lot of tools I have to learn. Snapmaker Luban is the tool that came together with my Snapmaker, but there are a lot better tools that I'm using as well. I learned to use Fusion 360 that I'm using for my CNC cutting. I use Sketchup to make the 3D-printing designs, and then import them in Cura to do the slicing. And for the characters and symbols to be cut by my laser, I'm using Inkscape.
So, that's my story so far...