Upgrade Question

We are preparing to setup a new LPAR and I have an on-going battle with
management (surprise, eh?).

Three options:
1. Load the new LPAR with 7.2 (our current O/S) and not worry about it
being no longer supported after 4/30/21.
2. Load the new LPAR with 7.2, then later, do an upgrade to 7.4.
3. Load the new LPAR with 7.4 (and then load the backup created from the
7.2 system).

Obviously the first one is stupid, but at the moment their one of choice.
The third one is the right choice, but they don't want to have to do
regression testing after loading to make sure everything works on the new
LPAR. The middle one gives them a new LPAR that will run immediately, but
later bite-the-bullet on upgrading and ensuring all the applications still
work.

Here are my questions.
1. Those who have made the 7.2 to 7.4 jump, after all of the vendors say we
have compliant software installed, have you had any issues? If so, what
kind of pitfalls would be ahead?
2. What was your system outage time when upgrading from 7.2 to 7.4? I am
trying to use this to leverage the third option that they'll have a future
extended outage if they take option 2.
3. Any other issues anyone encountered during either a clean 7.4 load from
7.2 backup or during a 7.2 to 7.4 upgrade?

I would have thought that all of the enhancements (both security and coding)
and the loss of support would have been convincing enough but, alas, I have
yet to succeed in selling them on option 3.

As always, thanks to all for taking the time to share your experiences.

Steve Meisinger