A few random thoughts:
- If architecture and museums includes interiors, in case you don't already know this, it's worth pointing out that some of them are very dark inside even during the day (The Madeleine, for instance, has no natural light at all except a couple of skylights), and some won't allow a tripod (even if they did, in the more popular ones you would get in the way); so IS or fast lenses that perform well in low light wide open, esp. with coma (the candelabras in Notre Dame create coma from hell with lesser fast lenses like the 28mm 1.
, would be helpful (your Sigma would be good, though it's probably not wide enough).
- The same applies to walking around at night, of course - which, at the risk of stating the obvious, is something you'll want to do: much of Paris looks marvelous at night.
- Do you have experience carrying several heavy lenses all day? The last time I was in Paris, with my 5DII, I found that if I took much with me, after a few hours of walking around I was almost ready to toss it all into the Seine and ended up taking just a couple of lenses with me, if that, when I left the hotel - 17-40 and/or 24-105 and/or 70-200 f4 IS during the day, with one or two faster ones for night or when I planned to go into somewhere with low light. I would hate to carry around the 70-200 2.8 IS II all day and suspect that when I return to Paris in a couple of months I'll take only my Sony A7r with a couple of primes, and maybe some of my Olympus M4/3 - I probably take better photos when not worn out by lugging stuff around. But that's me - you may be in far better physical shape!
- For my taste, the most attractive parts of Paris are the narrow streets in the 5th & 6th Arr. on the Left Bank; a fairly wide lens would be useful for that (plus, as someone else said, something longer for the gargoyles).
- Maybe I'm lucky, but I've never had any security/theft issues with cameras (or anything else) in Paris, despite carrying around a 5DII + 70-200 f4 IS in plain sight for hours on end.