As a guitarist and bass player, I've approached writing songs from both sides. Writing guitar to an already completed bassline is a unique thing, and kind of hard to do well. Just the same, there are some bands out there that have successfully shared songwriting duties between bass and guitar. One such band is The Minutemen. You can tell Mike Watt wrote some of those songs and the guitar was added afterward around the basslines. Feel free to list some other bands where the bassist was a prominent songwriter.