Perhaps I have missed something here -- I don't think I've seen the entire thread -- but perhaps you could achieve your objective by placing the following line at the beginning (i.e., *first* line) of your shell script:
#!/usr/local/bin/osh
Then your entire shell script will (should) be executed by osh.
I wouldn't really know, though, as I have never seen a system where "osh" was actually used. Usually I set the "ulimits" appropriately high for *all* necessary users, and pretty much every database server I have seen in years does the same...
(Actually, I usually set the ulimits for *all* users on the database server, but in my universe, only DBAs and sysadmins ever login to the database server. Usually, at least. With modern UNIXEN where kernel resources are allocated dynamically, there is much less reason *not* to do this than there was 10 years ago...)
Anyway, this might work for you. Good luck.
-- Cheers, -- Mark Brinsmead Staff DBA, The Pythian Group http://www.pythian.com/blogs