MH 653 did not dive at 30000 fpm, as per the FDR it did a series of stall and recoveries(consistent with A/P off and no pilot intervention...there were 3 shots ...so appearently the hijacker shot himself too)
The boeing 737s(200s and later variants too) hidden bug was the rudder hard over problem.
IMHO it is statistically very unlikely that there is yet another bug waiting to bite.
An interesting descent profile comparision would be with the Egypt Air 767 suspected siucide/mass murder.
By the way that suspect was also ex-milatary
What would make the 737 safer would be a flight envelope protection system like on the airbus family.
The Turkish crash on approcah at Amsterdam is the latest 737 stall down accident.