This is patently wrong: if I'm running self assembly from SMF, that has nothing to do with IPS. If I invested the tremendous amount of engineering and funding, I could do the exact same thing from SVR4 packaging, which I have done in some packages. What do I need IPS for then? I don't! But wait, there is more!:
Back in the days of SVR4 packaging, the scripts had to be extremely limited in what user-land features they could use because they had to be able to run in many different environments, including a) two minor releases back (so, S8 for S10 pkgs), b) netboot, c) boot media. This was insanely hard to support
Auto- and thin client capability was ditched, so the very argument used to fuel this nonsensical course of action was made moot. And even with Auto- and thin client argument, that was not enough to justify the atrocities committed by IPS.
No thanks. If I can't have IRIX inst(1M) or HP-UX swinstall(1M), I'll stick with good old SVR4 packaging. Since Snoracle killed AutoClient and thin client support anyway, configuration management with SVR4 works wonderfully. I have my scripting in the immediate installation context for configuration management in tandem with SMF and it's great. IPS can remain an obscure packaging technology nobody's using anyway for all I care. And that is good so: it's a totally botched implementation of inst(1M) and swinstall(1M).
By deferring execution of pkg scripts, IPS avoids the problem altogether. Instead, the scripts can only run in the running OS instance on which a pkg was installed (or from which it was removed). This is much, much cleaner than traditional pkg scripting. So much so that I'm shocked this technique hasn't been more widely adopted.
That is exactly what killed the adoption of IPS and severely handicapped the adoption of OpenSolaris and all operating systems which were IPS based. I cannot believe you (plural) are still refusing to see it! As if the entire Solaris ecosystem didn't have enough adoption problems, this just piled on and made it far worse. To someone like me who grew up on and deeply, deeply cares about Solaris and illumos and SmartOS, it's absolutely infuriating. You made your own lives easier but it cost you the company (Sun Microsystems), and it cost me having to primarly work on GNU/Linux based operating systems these days. We all lost.
Empathy is still a core engineering value. With IPS, there was no empathy. All your customers wanted was more freeware bundled with the OS and automatic dependency resolution for easier patching, things which could have been easily added to SVR4 packaging. They didn't need or want someone's doctoral disertation implemented as an experiment.