You might want to include "Ikea" in the title of your thread so people searching GW Ikea topics will see your question. I don't have any Sektion cabs yet, but would think that what you're planning is certainly doable. If you're lucky the shelf will sit at the right height in relation to the drawer front underneath, if not, you'll just have to drill an extra set of holes for the MW shelf to achieve the same. Other than that there should be no difficulty. Plenty of people have done that with the old Akurum line. Good luck!

Our kitchen is not fully assembled yet (we're waiting on the countertop install) so we haven't fully fleshed out the drawer uses. We started by looking at work areas then made our best guess as to the most useful drawer combinations - not what was necessarily aesthetically pleasing. We found that 10-inch drawers seem to be the most useful. Out of the nine base cabinets there are nineteen 10-inch drawers (there is a tray cab with a door, and the sink cab with a trash pullout and a door). We did put a combo of 5-5-10-10 drawers in one cabinet. The 5-inch drawers hold utensils. In fact we just purchased the Ikea bamboo trays for those. As others have done, we also have two 15-inch drawers for appliances. In only one instance do we use an inner drawer. That's the spice drawer where the 10-inch holds the commonly used spices and the inner holds the less often used items. Our rule has always been "open and get", not "open, open, get" - way too inefficient for us ;-) As an aside we found that the Ikea Variera spice trays do not fit neatly in a 24" wide cabinet drawer (which was disappointing). We'll probably end up with non-slip drawer mats.

The answer, is "it depends". You may need them for clearances. The Electrolux ranges for instance need a bit of a filler and a cover panel. This is where you have to read the appliance specifications. You do not need them for counter support though, if the rest of the design properly provides for that. Any exposed cabinet side needs to be finished with cover panels, and that thickness needs to be accounted for in the design. Any uppers adjacent to a hood will have exposed sides. If exhausting is not possible, and you are left doing a recirculating vent, I'd urge you to choose a hood both wider and deeper than the cooking zone below. You want the best capture area possible since you will not be able to exhaust the effluent.

Cant happen without a very firm steel attachment to the floor and steel all the way around. Even a cabinet under it would need to be attached to the floor. Cantilevering that much Stone out from a wall would require completely reengineering the wall and lots and lots of steel.