I looked at Lacanche and found their smallest unit came in at 27.5". I looked at induction and found the smallest cooktop at 23" from a brand I don't know; and that was just a cooktop. I found plenty of wall ovens at 24", though. Maybe you could use a countertop oven with a small induction cooktop? The Breville one is quite roomy actually.

I looked at induction and found the smallest cooktop at 23" from a brand I don't know

If you have the budget, there's a 20" aga induction range, although I believe it only has one cooking zone.

But first I would do your plan and decide whether you can really only do 20". If you have room for 24, that's actually a lot more real estate. I believe someone here has the 24" gas verona range and spoke highly of it.

You could also do cooktop over wall oven. There are plenty of nice 24" wall ovens, and possibly you could go larger than 24" with an induction cooktop since you can use that as extra workspace when not in use.

But I would definitely start by posting your plan in the kitchen forum to make sure you are using the space most effectively before you buy any appliances.

For squoodging a lot into a tiny kitchen, look at Janie Gibb's clever tiny NYC kitch, for example:

In this thread in kitchens:

http://ths.gardenweb.com/discussions/3615650/wanting-a-corner-sink-but-no-ikea-option-help-please