How do airlines handle SIGMETS?
Your options, as you pointed out, are either to climb over this area, To go around it, to go under it, or wait until the segment expires or is expected to subside.

Another option available would be taken by this information with PIREPS.  What are pilots reporting happened to them in this air space at this time?   The SIGMET noted that there was occasional severe turbulence expected in that area which is pretty vague.  If there are a very large number of PIREPS widespread throughout that block of airspace, it’s a good bet that it is very turbulent throughout and may not be a good idea to penetrate it.  If the PIREPS are few and don’t repeat much turbulence in that airspace, then it may be advisable to fly through.  Just keep the speed at that recommend by the manufacturer for penetrating turbulence and keep the fasten seat belt signs on.