I have ulterior motives in thinking about this ... ie maybe this can give me those flavor numbers for my Marshalling Troop / Oath of Fealty (Warlord Practice)
Old school Knight is a level 1 4e fighter of course but it wasnt a landed one.
I estimate the roundtable knights a bit higher (aside from wierdos like other PCs) in 1e terms most Roundtable knights I believe had their own estates and castles and followers and it took a lot bullying and impressing to get them under the Dragons Banner, I think we can use the Name Level == Paragon.
I think you estimated Arthur Close but I am going a couple levels higher (say early epic) . Epic Destinies on board by the time he was dealing with that many. (100+ roundtable knights)
A fireteam I was thinking were like 4 or 5 sturdy 2 hit minions or the squad as 10 normal minions. And that many can generate 1 success for a challenge of their level. (Heros and heroic effort is pretty awesome) ---> if that works we have our numbers.
Arthur deciding to use his Oaths of Fealty / Marshalling Troops practice in an at level challenge like hunting for the grail - perhaps those 100 knights are 25 fireteam worth of characters which are 10 levels lower than Arthur (and the skill challenge).
Technically one could get fewer of those with their own followers backing them handwave handwave for the war between Mordred and Arthur. Arthur got only part of his round table but this wasnt a holy quest and they pulled in their followers and so over all potency could still be analogous to the Grail Quest forces
I am thinking flavor math here... you complained about the somewhat more rigorous math
All I am shooting for is the "Hey that kind of works feeling"