Actually, in the Conquests i think you can research techs that are not officially in your tree, and even trade all those after the first (in each age.) Right? Imo, this isn't an exploit - your open-minded leadership is embracing new ideas and weapons as needed. Perfectly natural.
As for the Huns, their starting location is lousy, but if you herd them all a coupla turns further west, you'll find a much better land, flowing with milk and honey....

But historically, should the mobile Hun horde be tied to the same sedentary towns and farmlands as everyone else?
I like playing the Anglos or the Franks; they're quite similar really, since after the one conquers the other (usually while the innocent AI army is off fighting in the east...) you have western europe and a decent empire. Moving the capital is almost a necessity for the Anglos, but a MGL can ease the pain.
The problem with a non-central position is that the farther Roman (in this case the Byz) can win before you grow, expand, conquer a neighbor, develop heavy cav, and defeat the closer Roman. Bribing the other barbarians to fight the Byz can hold them (both!) in check, and keep them busy away from your lands. Do this often in the mid and late game.
And watch the Celts. They have an amusing ploy of sneaking a settler onto the mainland just before a peace deal, then surprise, they have a foothold that you can't attack for 20 turns.
