Actually, they do have a playable Charlemagne. Two of them, actually, but they're only in Fate/Extella Link.Knowing the proclivity of the Nasuverse, I look forward to a secretly female Ruler Georgette Washington and his cabal of Masonic wizards sealing in some great Beast under DC, via the architecture of Foreigner Pierre L’Enfant.
Maybe toss in Dumas?
I'm actually surprised they dont have a playable Charlemagne yet.
I'd like to see what they could do with Don Quixote and summon windmill giants, myself. Bonus points if they end up looking like the Nether Gundam.