As you know,
/proc/sys/kernel/core_pattern is system-global, and Linux-specific (not portable).
I don't think there's a facility to customize core dump filenames on a per-process or per-uid basis, but you might be able to to achieve what you want by sending core dumps to a handler program instead of directly to a file. By doing something like this:
echo "|usr/local/bin/my_core_dump_handler" >/proc/sys/kernel/core_pattern
my_core_dump_handler will be executed each time a core dump occurs. It can read the actual core dump on its standard input and write it to a customized filename of its choosing.
BTW: Your question talks about
/proc/sys/kernel/core_name_format. I am assuming you mean
/proc/sys/kernel/core_pattern because the former doesn't exist for me.