If the bulb fails and outer glass envelope becomes detached is there a safety issue with the inner exposed wires between the small inner bulb and the bayonet cap?
Yes, there are safety issues.
Firstly those wires are connected to the cap of the bulb which will be connected to the mains.
Secondly the outer cover acts as a UV filter, so if the halogen bulb is still working but the outer cover has come off the bulb will produce high levels of UV which are bad for your eyes.
You should treat the bulb the same as you would treat a conventional incandescent bulb whose glass envelope has broken or fallen off. Isolate the circuit (do not rely on lightswitches for safety isolation) and then carefully remove the bulb.
Risks include electrical shock from the more exposed wires, UV emission and possible injury from shards of hard glass or quartz if the pressurized capsule ruptures.
Aside from the other issues, the operating surface temperature of the quartz or glass of the halogen capsule is likely high enough to ignite flammable materials. So it is potentially a serious fire hazard.
More in this NEMA document entitled
Tungsten-halogen Lamps (Bulbs): Ultraviolet, Rupture, And High Temperature Risks