Working in Areas with Poor or no Cellular Availability

I often work in areas with poor or no cell coverage. My dilemma is that I don't have the ability to upload/save a Mission. Example, My last job I went out and walked the boundary area to fly and put in my GCP's. As I was doing this I would be creating my mission box to fly based on my location shown via GPS. Once I got to my home point where I was going to fly from, I started up the RC, DJI app to do pre-flight etc. but it would not connect since Map Pilot was open and connected to aircraft. I had to close Map Pilot in order to run DJI first. Unfortunately I couldn't do the offline map download feature since I had poor cellular reception. I lost the mission by closing the app. Once connected again with Map Pilot I guessed at my mission area and did the first battery flight 1. Once completed my iphone was dead due to the cold weather. I had to charge it up in my truck before the next flight (battery 2). Again I lost my mission including the abandonment point etc... I had to guess again at where I flew and created a new mission to complete the job. Is there any way that the Map Pilot could somehow save the mission within the device rather than rely on a network to upload to? I love the app, its an awesome tool but the lack of ability to save the mission before and between flights is causing me some grief. Most jobs I can't pre-plan the mission where I have wifi or network, I have to be on the site to plan what I"m flying. Any suggestions to how I can do this?