>Group is established for liking story and being fairly ignorant about mechanics
>new player joins for new campaign
>new player makes a character that has a good story/character but is clearly optimized far better than the rest of the party
>GM asks if that player help make the rest of the PCs optimized so there is no big difference in power/usefulness
Is this a reasonable solution?
It's completely reasonable.
>>55012866
It's not a bad solution, though it might be good to discuss what to do with the player in question rather than just ask him to do that. If he isn't a sperg and you talk with him about it he would hopefully do what is best for the group, even if that meant taking a slightly less optimized character. Or he could help bring the other players up. Both are fine, but it's important to talk about these things and make sure every one has the same expectations as one another.
The thing is if he can make an optimized character that tends to carry over into how he view playing the game, which may not mesh, so talking to him about what the group is going for can be important.