Matrix can take more than four departure airports, but that's probably a sensible limit for getting reliable results.

OP can search a few countries at a time with a multi-city on Matrix - only the departure point is limited to one country, so in multi-city you can put a range of end-points to hopefully find a decent ex-EU fare. Then you can switch that into the departure to get it both ways. Also worth noting that it's often cheapest to leave from one country and return to another - some of the carrier surcharge seems to go missing when doing an open jaw [I haven't worked out why].