Well then, I suggest you try to give us some sources at how long could a person fight in armour (and consequently, without) before it would significantly lower his ability to do so.
Besides if you noticed Crpg characters don't walk they run.
No, they don't. Well, not run as such. It's one of my gripes with warband.
To be honest, warband movement model is retarded. You can go on jogging forever, but you can't sprint ever (or run fast), and people can basically run backwards uphill while throwing/swinging weapons (wat), and they can run sideways too regardless of terrain.
I mean, maybe I'm a cripple or something but I can't run at 90% of my forward speed when I run backwards or sideways.
If you're bothered with "realism" issues in warband, then you could talk about feinting with long weapons (which have no inertia or anything), or movement model which is silly.
By the way, if you want to make armour more "tiring" to use, maybe we could discuss about how on earth do you kill someone in armour in 1-2 slashes? I'm fairly certain people wouldn't have went to great expense to make it if it was as ineffective as portrayed in crpg (ok, it's like that for gameplay reasons, but whatever).