I may have missed something in the earlier posts, but there are a number of issues here.
1) There may be slight logic differences between the CFM engine and the V2500 engine as fitted.
2) Unless both thrust levers are at least at idle then autospoilers, autobrakes and reverse on the selected engine are not available.
3) The spoilers would retract if TOGA power were selected for a go around.
4) If one thrust lever were left in the climb detent and the other retarded to idle or reverse on the call of RETARD would the autothrust disarm or would the aircraft remain in speed mode and maintain Vref. I think probably the later!
5) On a recent training detail (Sim) a FADEC fault resulted in an engine shutdown. As the command (ECAM) to bring the thrust lever to idle is generated by the FADEC( which had failed) the thrust lever remained in the climb detent. When the crew landed they became distracted because they only achieved REV in amber on the live engine and could not get the engine to spool up. More relevant however was the fact that the spoilers had not deployed and the autobrakes had not engaged. This was a situation the crew had not seen before and was confusing. Imagine that on a short wet runway.