I think that if the airlines is not "the be all and end all" for a pilot in this situation, and they are comfortable with accepting that the likelihood of becoming a millionaire in the airplane flying game is essentially zero, there is a potentially sound career in GA / regionals and that 39 is not too late to make a run at it - but it will require dedication, tenacity and humility. I gotta respect the courage, if the attempt is made!
There are some jobs in the GA sector paying well over 100K - and if it's doing the sort of flying you like, well, that's awesome.
Several GA operators are realising that stability in crewing is important and will try to look after their people in an effort to keep them. Uncommon it still is, but worth looking into. Mature pilots with the right training and approach to helping develop a business are a sought after commodity - and they are possibly somewhat more attractive if their logbook hours are behind the traditional airline "age vs experience" recruiting curve...
We'll see more of this in the years to come, I think.