FG has it's own computer language and the way it works offloading rendering is possible.
If I remember lots of XML code is used for descriptions and flight instrument designs.
Plenty of information in the development forums.
The Pi4 has a bunch of Uarts and these can be used as comms channels to instruments.
FG can use uart comms, I think I have seen Arduinos being used.
FG consists of a bunch of software, SimGear etc.
The terrain stuff can use GIS data and I have played with GIS software, about half of it will install and work on Pi4's.
3D terrain generation is of interest too.
For the aircraft models themselves, some guys on the Pi forums have shown Baked Textures.
That is a way to get more realist looking models on lower level hardware.
Blender is one common tool but we can only use 2.79 as after that OpenGL3.3 is expected.
I prefer Blender for Artists 1.0 which is an easier to use GUI for Blender 2.79.
We cannot use Cuda but doe300 has made a simple OpenCL on the Videocore4.
The Videocore6 should be able to do OpenCL but it is mostly undocumented.
Python based Videocore6 might be useful for some things.
Compute shaders are nearly here with external parties working with RPT.
GLSL shaders now work and I have been playing with them to understand them.
Have tested them in C, C++, Rust, Go, Free Pascal, BBC Basic, Python.
Mostly been looking at cloud and water effects and trying to figure out how to make them go faster.
There is some realistic shader cloud code out there now, but we don't have top end Nvidia cards.
Even my work PC struggles with some., but they look so cool.
I hope to learn enough to one day understand those research papers.
Been getting cloud books from the library and learning the names and characteristics.
I so want to do fog in landscapes.
WebGL works well in Chromium and plenty of code runs now.
Kodelife and The Book of Shaders are shader live coders that work on Pi's
Good for testing code quickly.
WebGL/HTML is interesting as those FG tablet instruments do it that way.
Running a browser on a Pi4 should be a faster way to get up and running.
Lots of code bloat but not much different than what guys have already done.
I have moved to Gentoo64 for my development Pi's and Gentoo64 comes with DistCC.
Not sure how to use Distributed Computing to do this or if it could be used.
Lots of bits now work and can be used, but there is so much to choose from.
As you say, so much to learn and I have allocated 5 years for it