Running two separate customers in a single partition with complete isolation

Many thanks to everyone who has take time to reply to this....please let me
re-iterate one or two things...

The 'saving' to be made is the management charge from the 3rd party hosting
company....the hosting companies charge a management fee on every partition
so fewer partitions mean fewer overheads which mean the offering will be
more attractive to smaller shops.

This offering would be aimed at any new, small, customer who has either no
IT staff or no desire to manage IBM i.

I appreciate with certain restrictions put in place a solution is possible
using standard IBM i a security.

I am against this approach and have recommended that my company adopt a
dedicated partition per customer approach until such time in the future
that we can add the necessary restricted admin functions to our software
product to make it a true 'SaaS' product. In the meantime though I have
been asked to see whether a tool such as I described exists as our sales
dept. believe the cost of a dedicated partition would be prohibitive for
smaller prospects.

In summary it's sounding like no tool is available and the only solution is
to tightly configure and manage in built IBM i securities....iASP's will
offer segregation library wise.

Thanks again.