Not worrying about conservation makes the task easy... I'm assuming that laser-hobbyiest math is at work here (outside of the surplus market, normally big diodes are more expensive than simple current control drivers)...
Diodes pop just by staring at them wrong, but higher power diodes tend to be
more friendly... It's not common to find optical feedback on higher power
diodes. The space between Lasing threshold and Max power on bigger diodes tend to be friendly as well.
1) chart each diode by the current and power output. Mark the current of lasing and when it reaches rated specifications. Remove from the pool any diodes that popped or are sufficiently out of spec.
2) order the diodes in series so that the more efficient diodes are further down in the series...
3) slowly bring up current and make sure that the current never exceeds the lowest spec in the bunch.
4) If the highest output laser is outputting lower than the rated laser output, bring up the current very slowly until the highest output laser reaches rated power.
At this point the system should be reasonably working... It'd be tedious with 6 diodes, but certainly not "hard"... This is the point beyond which you will be venturing into catastrophic failure territory.
5) Crank it up until right before the first diode pops... The trick is that we don't actually know when it'll pop. If you don't mind sacrificing one right off the bat, then take an "passed" diode from the testing earlier and slowly bring up current and measure the power output until the diode pops. Use that as a rough guide for max current and max power. In general I just recommend being gentle...
P.S. You'll only need 1 PBS to conveniently join all 6 optically in the way you were planning... Use a bunch of razor thin bounce mirrors.