DB, needless to say I strongly disagree with you on 2 points:
Firstly, your assertion that the order you have presented the different modes of flying in ATT is also the order of stability. Do you have any "proof" of that, or it supposition?
Then again, it depends on what you mean by "stability". Your mode 2 is very stable but also too slow for most uses. Mode 3 is quite unstable whilst you are doing the "push" bit, it only become stable after you have done the "beep" bit. I don't like this mode anyway because it brings the cyclic into the non-linear break-out force region as trimmed position is approached, and risks cock-up if an upper mode is engaged (beeping the datum, not the stick).
Mode 4 is the least stable on an EC225 (though quite stable on a 332L)
Mode 5 is the best for manual flying since the heli is moderately stable and as soon as pilot action ceases (ie pilot takes his hand off the cyclic) the current attitude is held. What's not to like about that?
I will also confess to not being a fan of your mode 1 other than when wanting to hold a hover and already being in the hover. I just don't like to feel the breakout region interfering with my control inputs during eg lifting into the hover.
My second strong point of disagreement is your last para regarding flying through an upper mode. It does depend on circumstances but for example a SAR pilot flying through HOV mode to finely adjust the position during winching is surely normal? And when you think about it, the basic autopilot gives you ATT which is effectively an "upper mode" of attitude holding. HOV is an upper mode designed to hold position. The new GTC mode is an upper mode designed to hold longitudinal ground speed (and definitely designed to be flown through).
So it is with GA - an upper mode that is designed to make the heli fly up and away - so if you want to fly it manually on departure but want an underlying mode that will get you out of the poo, why have a mode designed to hold a now-wrong attitude (ATT) when you have a mode that will save your bacon when you get confused (GA)?
The EC225 is quite happy to have you fly through any upper mode, whilst pressing the trim releases, and once you let go, it quietly, progressively and smoothly resumes doing what it was designed to do. Marc Salesse's team spent lots of programming hours making it do that, why not use it!
The problems arise if you fly through some upper modes without pressing the trim release, end up with the controls in a new an un-trimmed position, then let go and allow the stick to jump back to some old and now inappropriate position.