Can I trade with any non-hostile base on the planet?

You should definitely keep sending trade caravans to other factions, as this really allows you to keep up a good economy. You don't need to wait for a request.

Sending caravans out from your home, instead of just waiting for other tribes to come to you, helps keep up fluid commerce ... It's also cheaper than requesting traders at the comms console.

Source (emphasis mine)

Sending transport pods can be directed at any tile you like. Sending it to a tile which has your caravan will add the resources to their stock. Sending it to a faction tile will prompt you to land it at the edge or the center.

Pods can either be launched at a tile (including tiles owned by a faction), or at a caravan. Selecting a faction base prompts to drop at the edge or drop at the center, whereas selecting a caravan allows you to add the contents of the pod to the target caravan. Selecting a tile not occupied by a faction base will immediately launch the pod group.

...

Be careful with the landing site, as the pods can go through roofs; while they don't deal any damage directly, the collapsing roof can damage nearby items.

Source (emphasis mine)