What do you say about the following combination:
- Canon 600D + 50mm f/1.4 + 70-200mm f/2.8 IS II
- Panasonic GF3 + Lumix G X Vario PZ 14-42mm f/3.5-5.6 + Leica Summilux DG 25mm f/1.4
For the Canon the main thing I'd say is that such a combination won't give you much width, the 600D is a crop sensor camera so 50mm will give you the same angle of view as 85mm would have on your old SLR. Personally I'd consider either a wider prime like the Canon 28mm 1.8 or the Sigma 30mm 1.4 on a 600D or go for a zoom like the Canon 17-55 2.8 IS, if you really wanted a shallow depth of field maybe add a Canon 85mm 1.8 aswell.
What you don't say about your wife's use is how interested she is in image quality and manual controls. If she just wanted good compact quality pics in the smallest body possible and occasionally playing around with manual settings then the Canon S95 might suit her well. As small as a normal compact but with the image quality/low light performance of a bridge camera.
Alternatively if she did want the best image quality in a small package and manual controls what about the Fuji X100? Its only got a fixed 35mm lens but has crop DSLR standard image quality/low light performance in a reasonabley small stylish package.
I'm just thinking that if its you who really wants more versility on your camera then you might be better off getting a changeble lens camera and just get a fixed lens one for your wife.