I might be strange, but on average I cook for myself 4 nights a week, for myself and one other person 2 nights a week, and for a group of 4-5 1 night a week, and I try to shop once a week but at most 2 times a week because I really just don't have the time to go more often. This can vary week to week though. Usually, I set it for the 2-person plan for 5 or 6 nights, then I come up with my own plan for when I am feeding more people. This isn't a huge gripe and probably something pretty specific to my situation though. Mealime has definitely simplified most of my week in dinner and lunch planning.
Also, one thing that would be nice is if the ingredients needed were slightly more seasonal based. For instance, today I wanted to do the pork chops with peach salsa (it sounds so good) but no chance of finding peaches in my local grocery store, and I'm even spoiled being from the Bay Area.
I'm sure you have thought of this, but just in case, for modifications, you might want to be careful to take them with a grain of salt because of the differences in ovens, altitudes, etc. that can effect the cook times. Although that would be a super cool thing to incorporate if you moved into machine learning. Also, the second part is more of an idea for building in the future, I know it's a tall order so I hope you didn't take it as a critique!