Sadly, that's been done already. That was the "hero" name Croyd Crenson had in the Wild Cards series. He was called "The Sleeper"
because every time he went to sleep (every two weeks or so, for about a month each time) he would essentially reroll his superpowers. He had no control, and
never duplicated a form to my knowledge, although he often had repeating basics like superstrength.
Once, he even got every superpower in the entire book without any physical changes to his basic human appearance. Unfortunately God-Crenson was so powerful he
exhausted himself in only a couple of days and was out like a light before he could do more than be amazed at all the powers he had.
---
Those who fear the darkness have never seen what the light can do.
because every time he went to sleep (every two weeks or so, for about a month each time) he would essentially reroll his superpowers. He had no control, and
never duplicated a form to my knowledge, although he often had repeating basics like superstrength.
Once, he even got every superpower in the entire book without any physical changes to his basic human appearance. Unfortunately God-Crenson was so powerful he
exhausted himself in only a couple of days and was out like a light before he could do more than be amazed at all the powers he had.
---
Those who fear the darkness have never seen what the light can do.