From what I see, the only widget hasn't changed in years, and people have been complaining about it just as long. The 3x2 size doesn't make sense given it fits just as well in a 3x1 space.
There are three things I'd really like to see and one optional addition that would really blow me out of the water.
1. Change the size
2. Create a dark/transparent mode
3. Make a widget that only includes calories
Optional: make a widget that can include macros like you see in the top bar of the diary.
I understand the last one would be a lot more work, but the first 3 are definitely feasible and likely very easily done.