There are lots of "mixer" system that can be remote-controlled voa Wifo e.g. by a Tablet (Androd or iPad).
You also might want to look at the Behringer stuff. We use an X32, which is rather good quality for that price and very versatile but there are smaller systems as well.
->
http://www.thomann.de/gb/behringer_x_air_xr12.htm or
http://www.thomann.de/gb/behringer_x...d_rel_358424_0
Seemingly the XR12 does not provide multi-channel USB audio I/O, which is essenctial for working with Reaper. The XR18 is advertised to have "The incredibly fast and comprehensive 18 x 18 channel, bi-directional USB interface"
-Michael