Ah, I see that you're a Figure 17 fan. It's one of my favorite anime! I'm not going to go into detail praising it, but it did drop a drama bomb very devastatingly. I generally hate slow-moving slice of life series but I love this one.
He he! You never did the final Rank10 Windurst Mission?
Ajido-Marujido there uses Chainspell even though he's clealry a BLM, in fact he uses Chainspell + Ancient Magic. Well it's not sure whether he actually uses Manafont too, but he is a BLM so he should be able to, the fact that he doesn't run out of MP also suggests that ^^;
Anyway Shantotto in Dissidia seems to be able to use chainspell too, look at the video on Youtube, her final EX move is a sequence of instacasted Ancient Magics!
I actually wanted to write: "Chainspell + Manafont = <death> <you can have this>" but it didn't allow me to write a sentence that long ^^;