I thought about putting this in the Halo: Reach forum, but I decided against it.. for obvious reasons. To the point, however.
Halo 3 introduced armour permutations and little smidgets of lore for those new looking armours. Designed to fill various roles that the default MK.6 MJOLNIR armour was either ill-equipped for or just ineffcient in, such as the EOD or EVA.
In Reach, this concept has been taken to the next step, with a huge gamut of new armour models available for use, and alot of additional lore for these armours, to S2's and S3's in the field.
So, let us ponder. What roles are left unfilled by the MJOLNIR program? What armours prototyped the ones we currently see in the universe, such as the SPI-lookalike MK.5[P]. Is, for example, full SPI armour compatible with the then-in use MK.5 armour and the later Mk.6?
What about other weapon's programs such as the GUNGNIR? That brought forth not only UNSC trooper/marine armour compatible shoulder guards, but a Mk.5/6 exclusive helmet to guard an operator against the Slaser's radiation/glare.
[Edited on 12.28.2010 8:49 PM PST]