I'm sure I'll come up with more, since I'm using Tinkercad so much, but the two features I'd really like to see are:
1. The ability to type in measurements, angles, etc., and
2. The ability to Tinker on my iPad, possibly with the pencil.
Im loving the app - it's so much more powerful than it appears!
oh - 3. The ability to upload larger stf files than 25mb