I'd love that too !!!
I had to modify imposm 2.6 to do it (not really simple), because the way it's coded the nodes ID are not a field that you can add to your DB (it's an hidden field). But I don't want to (can't) modify imposm 3 the same way (entirely rewritten in GO), so I have to use the 2 imposms in my projects...
There is cases where it's impossible to work without the IDs of the ways. For exemple, I wanted to extract the entrance of schools. To do that, you need to import the entrance=* nodes and the polygons of schools, and join the 2, but if you don't have the ID to make the correspondance, you can't know if this is the entrance of a school or of something else. And of course there is not always relations linking the 2.
The only other solution to do that that I see would be to test the equality of the point's localisation, but with the possible error / approximation this is something I refuse to do.