Personally, no, I don't want Jeremy Irons to play Frollo! My choice would be Malcolm McDowell! Jeremy Irons, though sometimes he can make for a great villain, always carried charisma and eloquence about him that made him always some what likeable even when he was playing villains! Plus his voice is that of Scar's, Disney fans will always hear Scar when they think of him and never Frollo! The argument with Kevin Kline playing Phoebus and Maurice is less valid, because Kline is not that well known for playing Pheobus, while Irons is legendary for playing Scar.
I also think that Malcolm McDowell has a much more sinister face and has a long established history of playing depraved villains and perverted creeps like Alex DeLarge from A Clockwork Orange and Caligula from Caligula (also a tyrannical ruler like Frollo). I'd rather Jeremy Irons play the Archdeacon. This is mostly because of his role as Father Gabriel in The Mission. I honestly think he gave the best performance of his career in that film and provided such a wonderful contrast between Father Gabriel, a kind and pacifistic priest, and Rodrigo Mendoza (Robert De Niro), a violent and ruthless slave hunter seeking redemption. Seeing him play the Archdeacon would bring back memories of Father Gabriel in my mind.