I'm no expert but have worked with resins quite q bit. Here's my 2p. As indicated above, various polyester (Bondo), epoxy fillers and other fillers stick very well to Bakelite. (Actually, they stick to the filler materials used in the original Bakelite.) This makes repairs quite easy, as long as you are going to paint the steering wheel afterward, all well and good if the rest of your car looks like it just came off the assembly line.
For the real purist, with a pristine survivor, the shiny repaired and painted wheel overwhelms the rest of the interior patina. A crack or two here might best be left alone.
Also would be interested to know what happened to elray's wheel above. From my experience, "offgassing" should not cause the deterioration of the original Bakelite or of common repair resins. The worst consequence of offgassing I've seen is tiny pinholes in otherwise cured and stable resin. Possibly a cleaner solvent was the culprit or more likely improperly mixed resins.
Tom