Yeah I figured out that time restart thing pretty quick. I just wish for a back breaking game. It's pretty satisfying trying to play without dying, as you can be hit several times. After you get past the first region it really starts picking up fast and I love it. If there are achievements at some point, beating it all without ever getting blown up should be one for sure.
Yes... Achievements have certainly been considered (at least for the Steam release - but one might as well implement local achievements for other builds, I suppose), and it would make sense to add some actual cost to the rewind thing, and/or some kind of reward for avoiding it, but I'm not sure how to go about it. Although it won't let you bypass anything, it's still kind of "free infinite retries" as it is.
On that note, I have some ideas for future versions, leveraging the rewind/replay system in a more interesting way. A bit radical, but it has been done before. :-)
https://github.com/olofson/koboredux/issues/560