I think your approach would translate quite naturally to other types of design. Products are familiar and accessible but perhaps other familiar designed experiences could work well at these younger grades too.
Assuming younger students will relate better to things they are very familiar with might things like the school uniform, their bedroom, a chat app for the school and so on work in a similar way? Some of the sketching approaches might differ and model making (‘lo-fi prototyping’) wouldn’t necessarily be at full scale but so many of the other things you mention would work really well.
I wonder if an exercise centred around tracing aerial photos (e.g. Google Earth) would help students relate to large scale plans suitable for landscape architecture and architecture? Some work on sections and elevations would help them relate to doing building interior plans and elevations. It would be amazing to see students design a whole precinct and create scale models that could be viewed together like a kind of model village. I saw something like this last year during St Paul’s ‘airport of the future’ exhibition. (I think it was Year 6 work, can’t remember.) They had filled a classroom with a model airport and clearly had a great deal of fun doing it.
Sorry to go on, your post. It just inspired some thoughts about design in other areas that are a little less familiar to me.