Oracle startup scripts Unix

I am looking to standardize our Oracle startup scripts across Unix platforms, including RAC and non-RAC SMP, RHEL, SLES, and AIX.

At first it looked like grid was the way to go, cookie cutter installs and srvctl configurations. However, unlike listener software, previous versions of oracle would need to have their own version of grid installed to initiate startups of those databases?

The alternative is a muddled dbora startup script with sleeps and multiple, non-standard versions, on the web. For that, it looks like one would need to write for the local enterprise, maintaining it across all platforms taking into consideration all variations existing and to come. That's the headache I am trying to avoid.