I guess it depends on how much walking space you want. In this current configuration you have quite a lot of space for moving around, but do you want that? I would personally go for an L shape to maximise bench space with one section at a different height for seating. Alternatively, you could just have a standard L shape with seating on one side. Either way it's going to be quite a nicely sized kitchen.

Mine has a sink, dishwasher, and pull out wastebins. All good. What I should have done was insist on more cutlery drawers and some pot drawers instead of under bench cupboards. Not a fan of underbench microwaves so didnt ask for one.

Have you looked at island range hoods? You can get ones that are flush in the ceiling or get extra long ones made. For example, Melbourne made Qasair will make to order. There is also the option of pop up ventilation units. They aren't the most efficient but will still help and sit flush with the benchtop when not in use. And even those sparkly recirculation units that look like a light fitting. I imagine they could be set lower as they are mounted from cables (I think from memory). That all said, I'm not a huge fan of a cooktop on the island. I worry that I might splatter all over my guests sitting in front of the cooktop. But maybe that's because I'm possibly a messy cook... Also I like a island free to act as a buffet when I have larger groups of friends over.

The darker the bench colour, the more marks it will show. We have a stone benchtop - a white with small flecks of grey and beige through it - easy to maintain.