I play in a three piece blues band. I use bright roundwounds, some grind on the bass amp, lots of ghost notes and percussive "noise" to fill in between notes played, and a lot of cooperation between the guitar player, the drummer and me.
The guitar player likes my bass playing and in this band, lets the bass and drums fill much of the space, and plays more sparsely than he does in his other band, which is a 4 piece. We work on the mix of what we have, and it works well.
There isn't the hole left when he does a lead, because he doesn't overplay during the verses. He also plays more horn vamps and fills in this band. His leads are worked around more sparse instrumentation.
We don't need another guitar or a keyboard.
I use "Greenboy inspired" cabinets I built, using a 12/6/1 and a 12 sub and having such a full, wide range rig really helps fill things out. I wouldn't want to play in this band using 15's alone.