I think it’s great to ride bareback. In some cases prominent withers are less of an issue with more padding such as bareback pad over 1/2 pad.
When my mare was rehabbing from back troubles, we were without a properly fitting saddle. I rode WT bareback every day for 2 months I think? It did wonders for my own skills. Unfortunately we were (and probably still not) not up to working on the canter without a saddle! It is fun to ride bareback but I employ a flat gel pad to help avoid my DWB/TB mare’s shark fin. 
