That's as far as I've gotten....I do have a casting list worked out, with 
its own twisted logic...Take a look and let me know what ya think:

Uther     = Martius
Igraine   = Queen Serenity
Morgan    = Beryl
Morgawse  = Zoicite  <This is the Male Zoicite, btw :)...note that Malachite
                      is Lamorak, who was Morgawse's lover in the Arth. 
                      legends>

Arthur    = Rei       <Why Rei?  To get the A-G-L triangle to parallel the
Guenevere = Mamoru     R-M-U triangle...especially since it let me use 
Lancelot  = Usagi      Chiba-Usa as Galahad :)>

Elyzabel  = Motoki         <Elyzabel is Guen's confidant>
Lionel    = Shingo/Sammy?  <Lionel is Lance's worthless Cousin :)>
Bors      = Ami            <Lance's pure and chaste cousin, not worthless>

Ector     = Grandpa
Kay       = Yuuichiro


Merlin    = Artemis
Vivian    = Luna           <Vivian is the Lady of the Lake who raised 
                            Lancelot and gave Excalibur to Arthur.>
Nimue     = Minako


Lot       = Mistress Nine  <Again, I'm open to suggestions.  I need a 
                            woman, preferably evil.  Lot was King of Lothian
                            and husband of Morgawse, who is Zoicite here.> 

Gawaine   = Makoto          
Gaheris   = Crane Joe      <Basically a nice guy...obviously the 
                            youma in him came out when he killed Mom...>
Gareth    = Shirokuro
Agravaine = Prisma         <Has dark version of Makoto's powers>
Mordred   = Kyrstiara/Catsy  <Has fire powers like her mother Rei :)>
            
            
                            

King Mark = Nephrite
Tristam   = Umino          <Tristam loved Isoud, but had to let his liege,
Isoud     = Naru            King Mark, marry her...this eventually led to
                            trouble.>
Isoud 
le Blanche
Mains     = Molly? :)      <Tristam actually married Isoud le Blanche Mains,
                            cousin of Le Belle Isoud>

False 
Gwen      = Alan
Flunky :) = Ann             <What's her name again?>


Meliagrant= Jadeite

Sir Bruce 
sans Pitie= ?  

Turquin   = ?

Balin     = Cyprine         <Balin and Balan were brothers...ended up killing
Balan     = Pikuroll         each other while disguised, not recognizing each
                             other...again, suggestions taken with pleasure>
                            <C and P slew each other towards the end of 
                             Sailor Moon S, were twins, tricked into 
                             attacking each other.>

Pellam    = Professor Tomoe <King Pellam is the grail king...Aka the 
                             Wounded King, the Fisher King...He needs the 
                             Grail to be healed.>
Garloth   = Kaolinite       <An Invisible Knight, Pellam's brother...Any 
                             SM villians who used invisibility?>

Elaine    = Demand         <Suggestions here...Elaine was Galahad's mother 
Dame                        who seduced Lancelot by impersonating Guenevere
Brisen    = Emaraude        with Dame Brisen's magic...I chose Motoki because
Galahad   = Chibi-Usa       he at least had vague romantic connections to 
                            Usagi, but other suggestions eagerly taken.>

Pellinore = Rubeus          <Who hunted the Questing Beast>
Lamorak   = Malachite       <Pellam's son, Morgawse's Lover>
Melodiam  =                 <Accused Gawaine of slaying Dad, was slain in
                             judicial combat by Gawaine.>
Aglovale  =                 <Another Pellinore family member, forgave the 
                             family feud>
Percival  = Hotaru          <Your reasoning convinced me.>
Palomedes =                 <The saracen knight, took up the quest of the
                             Questing beast>

Questing
Beast     = Questing Bunny :) <Rubeus wants that Rabbit :)>

Sagremor  = Haruka           <A Rash knight, noted for rushing into combat>
Dodinas   = Michiru          <His wiser and frequent companion>

Green
Knight    = Ranma :)


Miscellaneous Kings:

Ygraine's Husband = Duke Ourannos of Cornwall

King Leodegrance  = King Godai
(Cameliard)

King Bors         = 
King Ban          =

King              = King Hikaru
(Lyonesse)

Wife 1.           = Queen Misa
Wife 2.           = Queen Minmei :)