ways and means, I had trouble reading your post. So please forgive me if I make a mistake in my response.
But I think that you are wrong on at least two counts.
The first problem is that you balance PI only against Toughness. All that Recovery does is let you handle damage better. If you are immune to damage, then it is obsolete. There is no situation where Supernatural Toughness + Recovery is better than PI unless you take into account the ability to go without rest. Which is worth less than 1 refresh, and therefore not enough to balance out anything.
The second problem is that you see no problem with messing up high-level play. The game works at 18 refresh. I play it at 18 refresh. The only houseruling that's really needed is the ability to expand Toughness. So why would you remove that option? To benefit play at lower levels? Because pretty much nobody will let you take PI with a +0 catch at Submerged, and so this should never have any effect.
On another note, I don't think that it's easy to bypass Toughness of any kind. You can't make social attacks during a physical conflict, at least not under normal circumstances by my reading.
And on yet another note, may I take the lack of criticism for the lower levels of PI as a sign that I costed them correctly?