RC Craft Telemetry Module

So, I am going to enter the RC plane world soon. The aircraft is being assembled, but I would not be me if I would just take it and fly. In addition to my 10 Euro 5.8Ghz FPV cam/transmitter, I want to get some data about attitude, altitude, course, etc. There are solutions for that, but they are very expensive, and I want to avoid buying what I can do myself.

I am also going to use the same thing for my RC boats, as if you go out far away on a lake on a sunny day, I had some trouble seing where I head.

I also want to add a few low-prio channels to switch light, operate anchor winch, or a crane on a ship etc. These can easily tolerate some delay, other then flight controls.

So, my idea is:
On board there would be an Arduino Pro Mini, together with a 433mhz bidirectional module (SI4463). It would get a GY91 board over I2C which has a accelerometer, magnetometer, gyroscope, and pressure sensor on board, so I can get attitude, height, course, all in one. Remaining pins could be used to switch something, alternatively a I2C or SPI expander could provide more pins. I might consider to place a GPS module there, too.

On my radio, I would add an Arduino Uno or Mega with following gear:
ILI9341 screen, 320x240 resolution. This would show the items with normal dashboard pattern (attitude indicator, height above ground, slip-skid indicator, airspeed) and would be mounted below the FPV receiver. It will also get a compass module, and if using GPS modules on both sides, I could indicate relative position and orientation of the plane/boat too, as well as distance. Remaining pins (in case of Mega) would be used for lots of buttons, joysticks (xbox 360 console spares, 2 potentiometers + button), switches...

So, the reason for your post is? Bragging? Stuck on something?

The reason is a kind of build log, where I could also get feedback, suggestions or tips from others. If its a wrong forum for that, then please move.