that is an interesting one Texanbar (btw if you are looking for an answer, dont read this any further!

) as I have considered similar possibilities.
If we treat this as a balance sheet, then for offering them 10% in F&F is, as you say, peace and quiet in the future.
However, there are three fair sized debits imo
1. getting there. If you or I were to offer Egg 10% would they accept? OK, they might/ might not, but I would be willing to bet that they would treat this as an "opening offer" and that you could be bid up the way. So strategically it might be better to go for say 2% at the outset, let everyone have a good laugh, then go to 5% and very reluctantly go to 10%.
2. it would have to be done very carefully - more "there is a dispute between us about the debt you allege there is between us. You know you cant produce the paperwork to enforce it, and I am fed up with your harassment. How about I give you 2% in full and final settlement and you go away and dont bother me any more". Also, it shouldnt give the impression of "a sign of weakness". Like you and Chris I am getting threatened with Court action by Egg. I am not really bothered about this, as their paperwork has at least five fatal errors in it. But I could do without it. That is why you are thinking of giving them 10%. That is why they continue to harass us when they have no legal route of getting what they want - that we will get tired and give up for a "quiet life".
3. why should we? I havent actually done the calculation - I might end up topping myself - but I would bet whatever money Egg have loaned me, I have paid back at least once, almost certainly twice and maybe even three times. Why should I pay them some more when they are so incompetent that they cant even get the basic paperwork right? I know there is a big issue (rightly) about not encouraging the avoidance of debt, but what about when that debt is just basically unfair, and in any event, they have no legal recourse to make me pay? Only harassment and how right is that?
Oh and btw, they still cant spell June - I got my letter today. So you should be in the queue before me.

Oh yes, one more spooky similarity. They phoned me on Saturday to tell me I was getting the Trevor Munn solicitors letter threatening me with court (something to do with the passage of time - they never seem to give a coherent rationale for anything that they do or say they are going to do - why cant they just do it, or say they will? It would save them making up quite so many lies). So this morning Trevor's letter (of 26 Jun) arrived, but about 4.30 one of the ARC goons phoned to ask me what my response was to their letter of 11th June (this more or less says - in the face of a detailed analysis of the claimed CCA - you've got the paperwork, pay up). This call was unnecessary for two reasons
A. they have already sent me the Trevor Munn letter
B. I replied to this letter the following day (12th) so they know.
In other words, basically this is just harassment. I have consistently told them I wont deal on the phone - they even acknowledge this - but there is always some totally unbaked excuse why they "have to do this" - like on Saturday, "we have to advise you of the letter that will arrive on Monday" - no you dont, you are just at it - AGAIN! That Texanbar is why its worth paying something to get rid of them. At the same time THAT is what they are relying on , that this kind of behaviour will exhaust us and we will pay up.