I speculate that the order in which they are presented might be for practical reasons, ie going from gross (easy to reflect on) to subtle (more difficult to reflect on). Rupa is really obvious and directly observable. Feelings pleasant, painful or neutral are just one step more subtle, in that they don't have 'substance' like our body appears to have, but seem to be being experienced by
the body. Perception is fleeting indeed, and volitional formations...got to be pretty quick to catch them, too. Finally consciousness, which is the hardest to witness (as a discrete element) in my experience.
I've had some interesting experiences by asking the question when the mind is calm (having placed my awareness into my physical form), 'is form permanent or impermanent? if impermanent, is it conducive to ease or to stress (eg, when it breaks up)?...since it is impermanent and stressful (if clung to when breaking up), is it thus fitting to be called 'my self'?
...then taking up a pleasant or unpleasant feeling
I am having, diving into it, and asking the same questions...and so on for the rest of the khandhas (how do you observe consciousness, though?
) I'm just a beginner in this, so all of this is just my personal musing here...an expert will be able to clarify and / or correct what I have said...