Alternatively you could replace the props with deffkopta-style props, keeping the 'Bee-lots flyin' furtress' look.
I concur that 0.5
mm (or less) plasticard (Evergreen is also what I use) will be your friend for such a project. Also, you can make rivets on those by poking the underside of the plastic with a sharp tool, or for neater rivets get some 0.8mm plastic rod to cut small coins from, rivets really help ork vehicles hold together.

Thirdly, plane modelmakers will often get their hands on a 'line engraver' to simulate tight-fitting metal plates, by carving a line in a single plate. Might be a useful tool for your project.
Aim to have armor pieces and rivets all over the place, sharp edges here and there, like axe blades and triangles coming off trailing edges, big guns and a paint job with rust and flames.
Don't hesitate to look at orky aircraft here or on The Waaagh (another website, more orky) for inspiration.