Nibbida wrote:I've read some writers say that the Eightfold Path is not sequential, but factors that are simultaneously developed. Others however, make some significance of the order. If there is any significance of the order, I would think that mindfulness would be last, since that is the factor that leads to insight and wisdom.

Any thoughts on this?

Well, according to Patisambhidamagga (of Sutta Pitaka) TREATISE ON CONVERGENCE XXIII

The N8P, 37 factors of awakening happen in a quick moment. This idea is also implicit in many suttas where someone achieved all 4 paths/fruits within minutes or split seconds...

At the moment of the supramundane path: there is convergence of seeing, which is right view; there is convergence of directing-onto, which is right thought; there is convergence of embracing, which is right speaking; there is convergence of originating, which is right acting; there is convergence of cleansing, which is right living; there is convergence of exertion, which is right effort; there is convergence of establishing (founding), which is right mindfulness; there is convergence of non-distraction, which is right concentration. There is convergence of establishing (founding), which is the mindfulness enlightenment factor; ... [and so on with the rest of the seven enlightenment factors] ... there is convergence of reflexion, which is the equanimity enlightenment factor. There is convergence of unshakability by non-faith, which is the faith power: ... [and so on with the rest of the ñve powers] ... there is convergence of unshakability by ignorance, which is the understanding power. There is convergence of resolution, which is the faith faculty;... [and so on with the rest of the five faculties] ... there is convergence of seeing, which is the understanding faculty. There is convergence of the faculties in the sense of dominance; there is convergence of the powers in the sense of unshakability; there is convergence of the enlightenment factors in the sense of outlet; there is convergence of the path in the sense of cause; there is convergence of the foundations of mindfulness in the sense of establishment (foundation); there is convergence of the right endeavours in the sense of endeavouring; there is convergence of the bases for success in the sense of succeeding; there is convergence of the actualities in the sense of suchness (reality). There is convergence of serenity in the sense

of non-distraction; there is convergence of insight in the sense of contemplation; there is convergence of serenity and insight in the sense of single

function (taste); there is convergence of coupling in the sense of nonexcess. Purification of virtue in the sense of restraint is convergence; purification of cognizance in the sense of non-distraction is convergence; purification of view in the sense of seeing is convergence; liberation in the sense of freedom is convergence; recognition in the sense of penetration is convergence; deliverance in the sense of giving up is convergence; knowledge of exhaustion in the sense of cutting off is convergence. In the sense of root foundation, zeal is convergence; in the sense of origination, attention is convergence; in the sense of combining, contact is convergence; in the sense of being foremost, [217] concentration is convergence; in the sense of dominance, mindfulness is convergence; in the sense of being the highest of all, understanding is convergence; in the sense of core, deliverance

is convergence; in the sense of end, nibbana which merges in the deathless is convergence.

Same is said for stream-entry path and up to Arhatship.