Depends on the cabinet configuration under the cooktop. It might be possible to modify it such that ir will accept a range that is the same width as the cooktop. Probably will never look like it was ezxactly meant to be that way, but would get you by until you decide to redo the cabinets. The double oven cabinet might be more of a challenge. Really depends on the opening size, stile with, etc. You might be able to have doors made that would cover the double oven opening and then come up with some type of shelf supports along the sides.
You know when people convert a garage into additional living space? Even when they remove the garage doors entirely and put siding and a window up, it still looks like a converted garage - not bad, just not like it was designed as living space originally. I envision a similar situation with "re-purposed" cabinetry. Probably won't look bad if done right, but might not look like it was originally meant to be that way. Likely won't ever be evident to anyone but you and you will get the functionality and update you are looking for.

just my $.02, dean