Bowling is the unique art of cricket.
No two actions are the same and no one has the perfect action.
And, some players have been quite successfull at almost all levels with highly unusual actions which have defied convention.

And, this is where the old saying, "If it ain't broke, don't fix it", comes in.
As long as the action is safe and legal, don't tinker with what has proven successfull unless and untill the bowler has a lean spell.
The most important thing is to develop an action which is safe, efficient and legal.

As the ball and wicket deteriorate, spin bowlers come into their own, with loop, drift, turn and bounce.
Whatever style of bowling a player chooses, he should be encouraged to pursue it in an attacking manner. The idea is to make the batsman play at as many deliveries as possible.
Indeed, experimentation in the nets should be encouraged at all times so that the bowler is able to perfect a variation before trying it under match conditions.

Constant practice is essential to hone the various styles of bowling.