Yep but I'm guessing that defeats the point of why you are using LXC.
Yes, LXC is not ideal for this.
While you don't need a disk anymore for sharefolders (sharerootfs plugin lets you use a directory), there are still other things OMV does that require something that looks like a real machine.
I use the plugin in VM. It's a great pity that OMV is not compatible with LXC.
I don't think OMV has to run in LXC to a be a good tool. OMV in a VM works very well.
LXC has many advantages over VM - better work with disk space, performance, security, migration.