Custom coding of drone for specific flight control and override

I would like to hire someone who can recode the flight and gps software for a Cheerson CX20 2.4G quadcopter drone to the following: The drone needs to have a gps located 'home'. We shall call this gpsA and this will be a fixed gps location. (I would like to be able to relocate this gpsA location if needed and 're-save' it to the drone as its home) There will be a separate, portable gps transponder that could be several hundred meters away from the drone at its home position. This gps beacon will have a variable gps location 'gpsB' The variable gps beacon will need to keep a tab of its gps location and upon pressing a button/switch it needs to then start sending its location to the drone. It should continue sending its location to the drone until it it turned off. At this point the drone will need to climb to a set altitude and then travel at maximum speed to the variable gpsB, where it will then hover above at a set altitude. The drone needs to be manually overridable by a manual human controller. This manual control should then be able to move the drone from its gpsB hover to wherever the controller wishes. It should hover at whatever its own current gps location is until the manual controller moves it, or presses a control button to make it return it to hover above gpsB or presses a button to make it return to its home gpsA. Please ask any questions you may have Thank you Drue