I'll admit I've hesitated to even post to anything potentially as controversial as this topic/change, but oh why not!

First a little background on my own travel habits - I've held status on various airlines but due to change in travel habits, preferred airlines, location, etc., that status hasn't necessarily been consistent on just one airline over the years (and some years with no status at all). As such, there are times I "enjoy" the benefits of status, other times I'm flying on a premium cabin paid fare, and others when I'm just one of the other millions crammed back in coach - and because of that, my view on this is one of multiple positions.

With that in mind, the best pre-boarding system I've seen was on a VS flight departing from IAD where it was only allowed for those passengers who had pre-board specific tickets (either a separate pass or jacket - don't quite remember, other than it was a specific color). At the gate, the agent made it very clear in the announcement for pre-boarding that only passengers with the appropriately colored pre-board pass would be allowed onboard at that time. My assumption is that validating the need for pre-boarding was done at the check-in desk well before arriving at the gate. Watching the pre-board process on that particular flight, there may have been 4 or 5 people who took part in it... on a full a340!

Beyond the pre-board for those with disabilities, infants, etc., I've always believed the first group for general boarding should be the premium cabin(s) - whether a paid, upgraded, award ticket, etc., these passengers in one way or another are seated in what's supposed to be the "higher end" cabin where premium services are an implied benefit... including the ability to get onboard, settled in, have a pre-departure drink, and relax without having to stand in the chaos of general boarding (at least that's my opinion).

Of course there are the high-value frequent flyers with status (who may be stuck back in coach on a particular flight) and I can definitely see the value of allowing them to board near the beginning of the overall process - after all, there's something to be said about someone who has spent, flown, or otherwise suffered through enough to make status!

However, across all of the airlines (each tends to be a bit different), there are so many additional groups that have been added for earlier boarding - including the credit card holders to those who buy a one-off early boarding group option. Personally I made the "mistake" of paying for Premier Access once on a base coach ticket when not holding any status and even if it was only $1, I would have argued it's a waste of money when watching half the plane board ahead of you.

So here's my humble opinion for ideal boarding order:
1. Pre-board those who have been verified as needing the service (ie. disabled passengers and those with infants) BUT similar to how I saw VS handle it, where a special boarding card would need to be gotten at the check-in desk... therefore you'd remove not only the risk of a gate agent's time being wasted and being more stressed than they already are by having to argue with passengers claiming their children should be included but also the associated problem with the "entitled" bunch crowding the gate... basically, if you didn't have the foresight to INQUIRE about the service at check-in, then sorry - you board with your assigned group. I don't know why but it seems as soon as people get to the gate, the respect, patience and common courtesy go out the window and that's where it turns into a free-for-all.
2. General Boarding starting with premium cabin passengers - very simple, if you're in business or first, you're in the first group.
3. Those with ff status as the second group.
4. All the other "regular" groups.

Yes the one thing I've left out are the "buy in" priority boarding options (whether a one-off Premier Access purchase or that from a credit card) - simply because I think it's made a disaster of boarding on every airline that offers similar schemes. Granted it's a pipe-dream since I'm fairly certain no airline will give up the possibility of incremental profits that they make on these "add-ons" to base coach fares... but even looking at myself, if I currently don't have status (from genuine flying) with an airline, then why should I be special and jump queue? If I really want to guarantee I'll have ample overhead bin space and the ability to get onboard first, then it's simple... either I fly that airline more and earn the benefit or buy a ticket up front!

Finally, I do think for those who qualified in advance for pre-boarding should have it made very clear to them at check-in (when receiving the pre-board "pass") that they will be required to wait until other passengers have gotten off the plane... and perhaps have it reiterated by the gate agent when pre-boarding is called... as a means to reinforce the fact that this is not a "benefit" to be abused and that there's a trade off (don't think you're going to cut the queue and then hip check 30 rows of passengers upon landing to get off first). Yes I realize there are some who will ignore the "warning" and try to play the system, but I do also believe sometimes reiterating the trade off is enough to make people think twice.