Another one of my crazy tangential brainwaves…
THS Travel insurance: Aimed at sitters & provides all the stuff that insurers provide but with pet sitting emphasis. There are loads of us mature 
sitters, so there must be no upper age limits and pre-existing conditions should be accepted sympathetically. The multiple trip, annual policy must have generous periods of stay and none of those dangerous sport categories. Pet related injuries could be specifically covered (seriously, I have had at least 2 animal related bone breaks 
).
Any takers?