All winds are relative to the direction of movement, i.e. the green arrow pointing to the right is a tailwind, the red arrow pointing to the left is a headwind. Should we change it? Would you prefer switching between relative and absolute wind direction?
You can make the same stuff used in GRAMET (aka vertical cut of the GFS forecast). This will help users to avoid learning new symbology if they wish to compare both forecasts.
Throughout the chart, you will find a grid of wind symbols. These give you a lot of information. The circle in the middle shows the cloud coverage in quarters, in the above example there would be no clouds. The barb attached to the circle is the wind rose with the standard symbol. The above example shows 35 knots and 30 knots of wind coming from north. The magenta array shows the aircraft’s movement relative to the direction of the flight (hence magenta, that used as standard color in avionics to indicate flight track). In this example the aircraft flies on a north easterly course and would experience a headwind coming from the left. The number right to the wind symbol is the temperature, -47°C in our example.
Add a full-screen option to have more complete view.
Change the color of altitude marks (so they could be visible on dark & white background) and make them still at the same position (right now they shift to the left).
Route details should be editable with keyboard input & coordinates should be switchable in settings (from DEG°MIN'SEC'' to decimals XX.XXXXXX°).
Add an option to save routes in your profile and make them constantly visible (right mouse click/long tap on the route to hide or close it). At this moment if you hit 'X' on the vertical cut pane, the route disappears. You don't always want to observe the vertical part, because it 'eats' a big bite of display. That will be especially useful when you fully implement it into the app to help pilots get better weather visualization when they're in the air (see my next suggestion).
A copy/paste of my old suggestion suggestion:
The app lacks speed control compared to web-version and I also would like to see more frames per time unit (right now it refreshes with a speed of 1 frame/3 minutes). Maybe you can make another time period in addition to 12/6/1 hour, say, for the latest 15 minutes which will be the most frame-dense period (for ex. 1 frame/minute) ? When pilots are already in the air, they're interested only in very latest weather data and 15 minutes may serve this need well.
I usually fly at lower altitudes and can receive mobile broadband connection from time to time (depending on my location) and an option to reduce downloadable traffic is highly demanded. Maybe you can make an option to preload specific part of the map (just like in Google maps) and fine-tune overall downloadable traffic to reduce unnecessary stuff. Again, the goal is to receive fresh & updated data as soon as your phone/tablet receives broadband connection , because it may be lost in next minute.
These are just a very brief quick-notes. I'll try to thoroughly test it later.