Saber Cú Chulainn would be like...a more extreme version of Lancer Cú, methinks.
If Swords are ideals and Lances are fate, then a Saber Cú Chulainn is a the epitome of an "Unconent" Cú Chulainn. Where Lancer Cú is rather unconcerned with the Grail because he's already got what he wanted and is content, Saber Cú Chulainn doggedly pursues (pun intented) the Grail like he did the Champion's Portion in Fled Bricrenn despite still having the same basic "Fight People" reason for fighting Lancer does.
Maybe even make him another younger alt, like Proto-Cu, to symbolize how he's constantly chasing the fate he (but also more prominently and symbolically, his Lancer self) already attained.











