How do i get peasant to make night elf buildings?

[Entaiden]

It creates the intial base for it but cant keep constructing

Also, how do i make it a flying unit?

 

[Yamuraiha]

"It creates the intial base for it but cant keep constructing" <- Living Night Elf building kill Wisp on constructing, that why the intial base is created but can't keep construct. I duno how to give that ability of wisp to peasant, but I can give you an idea that you create a new Wisp and change the model file, shadow, sound into a peasant, then you will have a wisp with peasant appearance.
"Also, how do i make it a flying unit?" <- Edit the section : Movement-Type : Fly
If you also want the unit to become higher when it is moving edit the section Movement-Height : (200 for example).

 

[BRUTAL]

I'm not 100% on a solution to night elves structures being built by a non-wisp, but a potential work-around (if you haven't solved it yet) would be to make a custom building based off a non-night elves building, and then just change some object editor properties to make it appear like it is a night elves structure.

Also for the flying unit question, are you referring to making structures fly?
What Yamuraiha suggested should be fine if so.

 

[KaerfNomekop]

I think your worker needs to have the Night Elf race to be able to construct Ancient buildings.