I don't know about the collapsing part. But apart from the structural integrity, yes, it is possible to have buoyancy with rigid bodies. Actually, you wouldn't even need the gas.
See here
Actually, I am currently looking for investment to make a proof of concept of this type of airship with a certain types of light weighted materials :)
I found the following condition for buoyancy of a vacuum sphere:
$[1 - (R_{inner}/R_{outer})^3] \rho_{material} < \rho_{air}$
where $R_{inner}$ and $R_{outer}$ are the inner and the outer radius of the sphere, respectivelly.
$R_{outer} - R_{inner} = $ thickness of the sphere wall