Horn: Please check the intensity with the following two conditions. 1) Intensity (frequency in technical terms) after few seconds 2) Intensity once the brake is applied (say some other electrical load is applied). In both cases, intensity should remain the same.
Connected Display: Yes, either Bluetooth or Wifi connection is needed to connect with the mobile phone. These days this chip cost less than a dollar and it is much needed in the advanced vehicle. If the present model will not have this feature, then it will be a big miss from ‘future’ vehicle. Anyway, my suggestion is to design the next version of PCB with the same PCB size with BT/Wifi chip so that just board can be replaced for the present model for upgrading.