2 pax travelling together, is it possible to book 1x Eco Light and 1x Eco Classic on the same booking?

Not trying to game the system, they'll have one bag to check and don't want to have to pay for 2x Classic when they don't need it.

Seems a bit annoying to have to make 2 completely separate bookings, and worry about getting seated together...

PS - should add, I've already suggested they get two rollaboards, pack more sensibly, and go for 2x Light instead (!)