Would you be considering to rent a FF camera (such as the 5D II) and a 14mm f/2.8L II? The f2.8 is just about fast enough for indoors as you have known and the 14mm is very exotic on FF. This way you can come real close to your objects (i.g. group of people) to get an unique angle of view. If flexibility is the key then use the 16-35L on the FF body will give you real 16mm too, that way you can spare the 10-22. I guess the 16-35L on FF body will yield better IQ than 10-22 on 40D. The combo is faster too.


The 24/1.4 and 35/1.4 are good ones to try as well - I personally will not hesitate to rent if I need them.