The effects of coherently enhanced radiation reaction on the motion of subwavelength electron bunches in interaction withintense laser pulses are analyzed. The radiation reaction force behaves as a radiation pressure in the laser beam direction,combined with a viscous force in the perpendicular direction. Due to Coulomb expansion of the electron bunch, coherentradiation reaction takes effect only in the initial stage of the laser-bunch interaction while the bunch is still smaller than thewavelength. It is shown that this initial stage can have observable effects on the trajectory of the bunch. By scaling thesystem to larger bunch charges, the radiation reaction effects are strongly increased. On the basis of the usual equationof motion, this increase is shown to be such that radiation reaction may suppress the radial instability normally foundin ponderomotive acceleration schemes, thereby enabling the full potential of laser-vacuum electron bunch accelerationto GeV energies. However, the applicability of the used equation of motion still needs to be validated experimentally,which becomes possible using the presented experimental scheme.