When the launcher crashes there should be a troubleshooter option.
For example if the crash message is 'an unexpected error occurred' most of the time deleting the jre and offline folder fixes this, so that would be that the troubleshooter would automatically does, and similar for the other crash messages.
Also (I know this has already been suggested) but if you add third party mod and one of them makes it crash, make the crash message show which mod it is
#Troubleshooter
zinc prawn
jagged tangle