"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).
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.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory
I will be AFK for a couple of days you guys hold down the fort while I am gone. I will be checking in on my phone but that will severly limit me. Be back saturday!