So you wanna be an Imperial Legionnaire? That's cool and all. As an Imperial Legionnaire you probably want one of the two armors:
-Penitus Oculatus Armor
-General Tullius' Armor

Well here's the thing: you need to be a STORMCLOAK or a DARK BROTHERHOOD member to get either of those two armors - both of who are enemies of the Imperial Legion.

Kind of strange that only enemies of the Legion can get their two best looking armors, yet the actual Legionnaire players can't.

That's coss legion soldiers are not Penitus Oculatus and why would general Tullius give his armour to a legionnaire ?.

Nothing prevents you from offing a PenOc officer even if in Legion, as far as I know.

But you're right about Tullius' armor. The Dragonborn if anyone should get such prestigious armor after Windhelm.

I don't know, the PO doesn't appear unless you start the Dark Brotherhood questline.

Ditto about Tullius.

There's an outpost at Dragon Bridge, no?

Yes, but that would involve killing that menber.

And the problem is....? (LOL sorry )

Reverse-pickpocket.