Hi,
As far as Radha is concerned, I would say that both business and personal life are two different Extremes and one should not mix up the business with the personal life. If Avinash is so much worried about the happenings, It clearly shows that he doesnt have any work - Life balance. He need to be made understood about the situation clearly and Radha is promoted only for the reason that she is performing. Avinash should be happy instead of being worried to share that radha is a performer.
As far as john is concerned, Organizational politics would surely evolve in any organizational setup. It is the responsibility of each individual in the organization, to direct the organizational politics to a productive way.
Aslam, as mentioned, is a superior guy who would really would have worries in reporting to a person who is younger then him. This is where the issue of experience/ performance based appraisal system takes place. Aslam and every other person in the organization should be clearly explained about the metrics through which radha is promoted. There should be a transparent appraisal system. This would make aslam to actually realize the gap between his and radha's performance. He should also be motivated in a manner that he would also perform in order to get his promotion.
If Radha could carry out all these suggestions, I hope the situtation would turn out into a productive environment.
Looking forward for the others to comment and make corrections in the solution....