I would mostly agree to this point, there would certainly be significant effort needed and perhaps some sacrifice and that could be their way around the situation but.. if this is the reason, don't you think it would have made more sense and been a simpler task for SE and addressed many of the concerns to just rename classes to Jobs and make them more defined and unique?
The issue here is not what their intention is, but how they addressed it. I can't really see both systems being utilized properly but rather ultimately hinder each other. I really feel keeping 2 systems in place will just be a source of complication, redundancy and introduce future problems. SE is just opening a can of worms when the base Armoury system isn't even efficient and far from perfected yet.
To get this Job system of real use and value, alot of ongoing effort and attention will need to be poured into the battle system, mobs and content in general to make it worth using and keeping the old system just as significant.
To comment on the last part of your post though, since i have seen this reasoning few times already. I find it funny that on one hand the white knights are blaming the crying/whining groups for asking for and bringing in the job system..and then ironically enough, on the other hand they stand by this new duo-system like their life depended on it (because..well SE came up the new idea so it must be good), to the extent where they rush to flame such threads and throw silly anti-XI rants.
I disagree, i don't think it has anything to do with 'dumb' people, many players have complained time and again at how simplified this game is becoming, it doesn't take a genius to figure out how to slap abilities in their list and become a versatile player.
I think there are various other reasons why SE would think of introducing this. For one, the Armoury class is way too loose and undefined to be able to actually form a reliable party on the fly to tackle tougher mobs; Not only do we have a fail Party Search system, but to add onto that, the Armoury class exacerbates this issue further with an extra layer of Shadowiness and imperceptibility. I mean do you really plan to interrogate every player in a full party of 8 to find out their exact abilities before you form each party? Not only is it inefficient and impractical but can even come across as offensive when you plan to ditch a person because they are missing a certain ability from a secondary class.
Job system as in XI or FFT would never have this issue because simply put, they would just give away what a person can and can not offer by name. Granted, The new job system can address this issue now. Yet i still disagree with 2 systems in place as mentioned in point above. No need for complications, one simple yet deep system sounds like the smart and logical thing to do.
I really believe SE just needs to focus on fixing the core features of the game before expanding too far, i really don't think they can afford to risk taking more damage and lose whatever remaining players they have if more new features fail.
By their own words, this is their final chance to fix the game before PS3 release in hope of attracting the masses back, and so.. i voice my concern.