If you want a 36" later, you need to put in a 42" hood now. As far as cutting the granite goes, you're talking a couple of hundred dollars and a ton of abrasive dust that gets everywhere despite you trying to contain it. There may also be different electrical wiring requirements for induction as it uses more power. I'd want at least a 50 amp circuit there now, as doing that later costs more than when you have everything open.

if you think you wil be moving to a 36" i would do it now. sell your present cooktop on craigslist to recover some of the costs and apply it to the new one. also look for new one on sale on line or at scratch and dent sale to make it more affordable. perhaps by doing this you might still be able to get induction.

cutting stone is a tricky business. i would not risk re-cutting granite on site later and potential risks that introduces to what i am sure will be beautiful counters. the first fabricator did a major error on my marble which required the entire job to be pulled and re-done by a different fabricator. things can happen, don't take the chance!

In terms of needing a 42" hood for a 36" cooktop. I will be getting an undercabinet hood (not an insert) and the only real high heat type thing I seem to cook is bacon. Do I still need a 42" hood?

I guess if so then having the 36 hood with the 30 cooktop will be what I'm stuck with.

check the specs for the 36" and verify what hood width you need. i have a 30" all gas wolf and went with a 30" hood with the appropriate CFM's, works great, no issues.

Ok, talked with the cabinet guy today and actually the layout of the cooktop wall is better with a 30 inch cooktop so I'm going to stick with what I have. To the right of the cooktop is a door to the dining room (about 16 inches away) and if I had the 36 inch cooktop the countertop would go right to the door casing and also cramp the walk way. I do currently have wall ovens in that area so I could upgrade to an induction cooktop in the future because the electrical is already there.