i like the simplicity, it really allows a rapper to take control and with a strong voice it would fill out and compelete this track, i would work on maybe adding some additional instrumentation, ambience, and also the drum pattern could use some ghost kicks and some percussion for tension in certain spots would be good. That being said i would definetly wait until you get a rapper on this before you add anything, if you add too much the rapper wont have as much freedom, plus when you have the vibe they lay down you can base your additional sounds around that.