[Ballbarian]

#setland = Adds to the province.
#land = Kills everyone for a clean slate.

You can set the poptype while using either command, but #setland will retain it's original defenders. You might end up with a barbarian province defended by lizards. If you used #land it would kill the lizards but you have to manually add barbarian defenders or it will be undefended as you have found.

#knownfeature

If you use the numeric index you do not want it enclosed in quotes. Quotes are only necessary when using the name of the site. (Rusty memory: Wasn't there a time when we could not place magic sites by their index? Is that still the case? Or am I thinking of items?)