I'm not sure if it'll actually increase your chances or not, it might just add two more researchable stages to the planet exploration upgrade. However, for the planet bonuses this will be pointless as you'd have to mod every planet bonus so that it could appear in the two new stages. The easiest way to change artifact/resource chance is an option in the .galaxy map files, but obviously that would only apply to the map you changed.

Artifacts are coded in when the map is generated I believe. My reason for saying this being that surrenduring and then continuing to observe will so show all artifacts on the map, even those not yet discovered by other players.