Good stuff so far.
Building an arched roof could turn out a lot more difficult, but not impossible. The 'Belfast Truss' hangars were built as a double-arched structure, but the trusses (from which the name is derived) would be a complex item to replicate.
Here's some internal shots of the 'Belfast' hangar, showing the trusses, support pillars, doors and walls, and an internal shot of a 'T2' hangar.
Good luck!
EDIT: Note that, during WW2, the windows high in the walls of the 'Belfast' hangars, and those in the roof of the 'T2' type, were 'blacked out' by painting over them, sometimes internally with a dark blue paint, but more often totally black, with the outside glass painted in camouflage colours (or black on late war, overall black 'T2' hangars.).