The main hazard of icing is that the LE ice formation changes the aerodynamic properties of the wing. This will certainly reduce available climb rate, etc. as well as increasing stall speed. Other interesting affects, which will vary with aircraft type, include loss of AoA indication, tailplane stall, loss of pitch stability with flap selection, etc. etc.
If an aircraft is cleared for deliberate flight in icing, then there should be a section or supplement to the manual stating the correct handling techniques and quantifying the performance degredation. The correct answer is in there for a particular, but I can't see that sitting just above the stall, with potential for further icing and further increases in Vs is particularly clever.
G