Hi,
There are multiple process_exporter projects such as this one:
https://github.com/ncabatoff/process-exporter
I don't think node_exporter has any integrated feature for that (in
fact, even the systemd part is targeted to be moved to a dedicated
exporter).
On the other hand, one should have hope that RHEL6 is gone by the end of
the year when regular support ends... :)
Kind regards,
Christian