I did a live in this situation for an end-of-year show in a music school, we were in a bass+vocal/guitar/drums trio, only the voice was amplified by the FOH, at the time I was using a CLR powered speaker, so I used the CLR as a classic combo amp mounted on a table halfway up the back of the stage, as I was playing wirelessly I was able to do my balance myself .... to adjust the volume of the amp being directly next to the spectators. After the performance, I was told that the guitar was going well and was perfectly audible. So for me it was a risky but successful experience.
In this situation it is necessary to have a fairly powerful FRFR