Reaper isn't going to help him replace what BIAB does. I use Real Band and Pro Tools. Nothing that doesn't write backing tracks can replace Real Band. A DAW is a DAW. It depends on what you became familiar with. Reaper, Samplitude, Sonar, Ableton, CuBase, Logic, and for the OLD guys, Texture.... they all do what they do. Mix tracks.
Hate to burst anyone's bubble but DAWs are NOT all the same. If Realband was reviewed alongside modern DAWs it would not hold up very well. I avoid it unless I really need to closely control generation of RealTracks and then use it only to get the tracks exported as quickly as possible into a real DAW.