Yes you can set up a custom chart of any metrics you want to stack (my chart doesn't demo this as well as your data since the one interface in my set monopolized most the traffic, but you get the idea.)
There's also Perfstack that was added relatively recently, which I feel like does visualization significantly better than anything in Cacti or in older versions of Orion, but unfortunately doesn't do stacked data.
Is it possible to create virtual interface which combine IN port X + IN port Y ? (And OUT port X + OUT port Y)
In order to have alerting, i don't just need a graph