I’d say the top boys immediate followers would all be well armoured be they Teulu, Huscarls or whatever. Local lords would have all the gear too and so would their close associates but there won’t be too many of them. Most of the men they lead will come with whatever they can self supply with a minimum being spear and shield.
I’m currently doing the Retinue of Gospatrick of Northumbria for Lion Rampant. GoN and the boys have full kit. Then I have a unit mostly armoured fellows who are supplied from the royal religious bequests and sinecures. The rest of the host are un-armoured units each led by a couple of armored figures representing local lords and their free men. As Patrice says it looks better, as well as likely being more accurate.
Some times large forces of fully equipped men do take the field Penda’s invasion of Northumbria comes to mind or the Great Army in its heyday. Mostly though I’d go for mixed formations.
As to how to replicate the Swinton effect I think Comitatus would do it, as would my own, yet to be finished Piquet inspired Ends of Empire. In both cases you would keep allocating ‘action points’ to Swinton’s unit. If he get’s killed which is a risk his unit will fail, if not he pulled it off.
Good thread by the way.