How can I encourage alien expansions?

I made a map intended purely as a sandbox for designing factory layouts, with peaceful mode, rich deposits, and water only in starting area. Apparently I also chose (or effectively chose) to have enemy bases be rare and distant.

This is a problem now, because I need large quantities of Alien Artifacts for my research and production.

In order of most to least preferred, I'd like to know one of these:

1. A non-cheating way to encourage the aliens to more frequently expand (create new base locations with spawners) in peaceful mode.

2. A way to do the same which does use console commands.

3. A command which will create a biter spawner.