other ways to have brought back Spock?
time travel - Trek III couldve been like an 'undoing' of the events of the previous film in order to get Spock back
e.g. maybe if there had been no 'remember' or Spock coffin on genesis (as was originally planned – I believe those scenes were late additions) so III would be hijacking the Enterprise to time warp around the sun to save spock but on the way they encounter the klingons who are after genesis so proceeds with similar events but done abit different - david death, ent destruction, genesis blows up etc (all without young Spock) but for the conclusion/last half hour instead of vulcan/katra swap they use the captured BOP to go around the sun and end up toward the end of TWOK (like the 1955 scenes of BTTF2 & the 1984 part of Terminator Genisys) cloaking device on, beam aboard the Ent and encounter their slightly younger selves and they have to try to prevent Spocks death (Kirk and Co sneaking around like Trials and Tribulations, & like Picard/Kirk in Generations redoing the end of GEN), without interfering in TWOK events too much (although maybe Trek III Kirk couldve encountered Khan face to face this time - Montalban cameo), before succeeding in getting the mains back on line before Spock can sacrifice himself and then returning to their own time, and everythings fine and everyones alive again (like the end of BTTF/XM DOFP/Superman/MOTU etc) - spocks alive and well, Davids alive, the NCC 1701 Ent is ok and has its decommission ceremony