Please go through the following link herewith which will let you know regarding maximum possible inherently used band combinations & various important indices those govern LU/LC classification algorithms for sentinel 2. Indices based LU/LC classification is globally accepted & widely used LU/LC classification method where you can introduce multiple-threshold technique to achieve desire accuracy (GNDVI, EVI, NDBI, GVMI, NDWI etc. has greater influences). You may contact me for further details.
Please be informed-
1. In this case, if you use Band 2,3,4&8 alright. The moment you will use other bands you must sacrifice spatial resolution from 10m to 20m.
2. To escape this you may use Landsat 8 to limit your self within 15m spatial resolution merging PAN with MSS. As you know Landsat 8 comes along with 15m Panchromatic Band (Band-8)