I have had a couple of great ideas, although they will need moulding into something sharper in outline, but they at least form alleys of exploration for research and stuff.
I have settled on Christopher Columbus as my 'famous person from the past' - because Velazquez just doesn't interest me enough - he's no Leonardo. Too much religious art, and not a hint of Goya or Bosch to lighten it. And Columbus has not only all that wealth to play with, or be challenged for, but he also has all kinds of conspiracy stories around him - claiming he is not Italian in origin but Greek, Catalan, Portugese, a Spanish Jew, etc, etc. And he does have a rather odd signature, that no-one understands
I have managed to fill most of the roles that I outline originally, so I guess I need to get on with throwing them at each other, killing a few innocents, riling up the goodies, and emphasising how unpleasant the baddies can be. They've been a little comic or incompetent up until now, so time to turn up the heat.