From maintenance systems and standards side in oil / gas plant, what can be implemented to significantly minimize operating cost / maximize profitability?

CBM is one strategy, to improve availability while reducing cost you have to select mix of strategy depends on comprehensive analysis, example RCM or equivalent, as a result some equipment suite RTF other have constant wear which suit FTR, CBM will suit the random failure. etc... 

Condition based mainteance can decrease  the cost of mainteance and will increase plant availibility  along with profitability.