Madeline and Friends: Madeline's adventures in the Holy League. Never got past a cast of characters (Madeline, Pepito, and a Muslim girl codenamed Mitraille).
Catholintegra: Enrico finds an I-Jin of Gregor Mendel and tries to create a Catholic version of Integra. Dropped cause Caterina Sforza of Trinity Blood made a good Catholic Integra already, so it was retconned into an Iscariot in the far future being more successful in creating Catholintegra than Enrico was.
Let The Flames Begin: A Mirror Universe where instead of fangirls invading, flamers do.
A Proper Lupin III Adventure: Hellsing is recruited to stop Lupin III from stealing the Crown Jewels.
Hellsing Heir Auditions: Integra seeks out someone to adopt as her heir. Dropped when the Grand Finale of Hellsing reveals that the head of Hellsing will be a government-appointed position from now on, starting with Penwood's grandson.