I have a few corrections to your statements. The Tello does not use a "gaming protocol" to communicate. It uses TCP/IP over a WiFi signal. The gaming controllers do not communicate with the Tello. The gaming controllers communicate with a phone via USB or Bluetooth. The phone then communicates with the Tello using TCP/IP over WiFi.WiFi is radio communications. WiFi is just a word referring to band of radio frequencies (2.4 and 5.8 GHz) that has been allocated to wireless communications. It is also digitally modulated meaning the information transmitted to the drone and back is digital rather than analog. Being digital helps in many ways to eliminating interference from other sources. The Tello transmitter and receiver have been designed work with each other using a standard gaming protocol. This allows us to use a gaming transmitter to control the bird. Theoretically the RF portions of the transmitter and receiver could be moved to another frequency slightly above or below the allocated band of frequencies while keeping the modulation scheme the same but those frequencies have been allocated to types of services and you would be out of band.
So if you had a different transmitter and receiver that was designed for drones you might be able to get it connected to the Tello motors and provide some control of the drone. However, I would bet that transmitter and receiver would still be in the WiFi band of frequencies and you would not gain any advantage over the existing RF system currently used in the Tello.
If you want a better more reliable control system you need something like DJI's occu-sync (sp) used in the more expensive birds. Occusync with the controller uses 2.4000Ghz - 2.4835Ghz. occusync constantly jumping frequencies depending on conditions to avoid interference and it can even reduce its bandwidth from 20Mhz (full width) to 10Mhz (half width) to improve range and be more resistant against signal loss.. Even occusync is operating in the same WiFi band (2.4 GHz) as the Tello.
I am an RF engineer, meaning, I designed the radio portion (transmitters and receivers) of digital radios. There is a device that called a modulator the connects to the transmitter and de-modulator that connects to the receiver. It is in those devices where the magic of digital communications takes place. I am not a modem design engineer. That is another skill altogether. The RF portion of a radio is simply a pipe to get the modulated signal (information) through the air.
The Spark or the Mavic Air used with a phone instead of the controller both get 2-3 times the range of the Tello. This is from personal experience using the same phone for each of them. So I strongly disagree that the Tello has great WiFi. Having to use a WiFi repeater is a hassle that somewhat diminishes the great experience and portability of using the Tello. I would pay more for a Tello with better internal WiFi.Do you get significantly more range than that with a spark?
I just noticed that you are from Germany. That may explain the difference in our experiences. The US WiFi uses different channels and we're allowed to use a lot more transmit power.Do you get significantly more range than that with a spark?
The Air and Spark don't use Occusync even when flying with a controller.I have flown a Spark and an Mavic Air using a phone and they have similar range as the Tello when the Tello is using a WiFi repeater. When flying a Spark or Air with a phone, it doesn't use Occusync because a phone doesn't support that. I hope the next version of the Tello fixes a design defect in the WiFi implementation and we no longer need to use repeaters.