Supports are one of the biggest hassles of 3d printing. ABS supports are easier to remove than PLA, but they still require some precise work to obtain good results.
Even in cases of multiple extruders and materials they usually take some kind of chemical treatment and need to be applied layer by layer in the same fashion as normal filament. A solution to this problem would be to implement a secondary extruder that uses a material that is easy to remove as well as to be able to fill a multiple layers gap at once.
Our approach is to use hot glue as support material. It does not stick much to PLA when heated up and is easy to melt and reuse afterwards.
The concept is based on a secondary extruder of hot glue bars that fills the gap in large quantities so that even if the deposited material reach higher than the principal extruder, since the temperature of the extruder is higher than the hot glue melting point and the hot glue would deform with the deposit of new material.