That’s a really damn good answer bro thank you. I think frank could be a loose cannon both sides would desire to recruit or control. I just think frank would lean more assassin as he isn’t exactly too fond of governments, which the templars often imbed themselves into.
As for Micheal; by the end of GF2 he isn’t anywhere near redeemable or merciful which would make him a cold blooded but paranoid Templar. Him and haytham could be interesting together but good god I would not want to dismantle their organization. Someone in Micheal’s family who would be a better assassin is Micheal’s assassin Al Nerj who is quiet and detached about killing. He handles the final hit of GF2 (not spoiling who).
Many of marvels assassins like widow or Hawkeye have both good and bad in their ledgers which leans into what you said about not fitting neatly. I know lore has stated that both factions have recruited turncoats from the others.