We will see how the reroll strategy feels when playing. I assume that it is harder than rolling once with 70%, for the following reasons. First, I think the second issue (having only one mission) is more of a problem than the first issue (having no mission). On my runs on medium, I realized how much faster I could unlock the Majors because I had more options w.r.t. chosen Captain and destination. Here, the reroll will not help much. With the morning scene morale sink, having no mission at all is not that bad anymore, because you sometimes need a day off in any case. Of course, it's still annoying if your current location does not offer a good recreation option.
About the symmetry of the difficulties, I'm also not a friend of the 100% on easy. If easy should be tutorial style, you remove a part of the game mechanics here. I think 90% would be a better choice.
I still would prefer the 70% difficulty. It keeps stuff easy and easy to understand. But I can also understand your sentimal arguments. And before having played it with the reroll strategy, everything I wrote are just theoretical assumptions. So implement it, and we will see how it feels.
About this balancing stuff, it might be good to have a non-UI version with an AI interface, so you can write a simple AI that plays it thousands of time, maybe outputing some statistics, and you get a feeling where the game is too easy and where too hard. But I guess this will be hard to include at the current stage of development. Maybe for your next project.