Dear Rohit,
You have proposed the following methods:
Group Discussion
Presentation
In-Tray/Box
Final Interview
However, the above tools look good for external hire. This is because you do not know much about the person and you are conducting the recruitment test(s). On the contrary, here you have your regular staff. Therefore, their manager's views matter lot.
Secondly, have the internal candidates taken training on "Supervisory Develop Programme" or "Team Leadership"? If yes, then you may include points covered in the this training for the selection purposes.
Lastly, job of team leader is to get the work done from others. When you put on the candidate through "Group Discussion" or "Presentation", what you are doing is to check the person's communication skills. However, mere communication skills is not sufficient to get the job done. A good communicator on the contrary could be liability because these persons know very well how to cover their weaknesses. Please remember the famous proverb "talking parrot flies little".
In my previous reply, I had recommended you checking the worthiness of the candidates on the following competencies:
a) Technical excellence
b) Interpersonal skills/Feedback skills
c) Ability to foster teamwork
d) Conflict handling skills
e) Organisational communication
f) Customer orientation
g) Analytical skills (depending on the nature of the job)
On each competency, obtain the assessment of the manager for each internal candidate. Secondly, let each candidate give a presentation on:
a) How he/she delegated the work in the past
b) How he/she handled the conflict in the team
c) How he/she gave motivational support to his/her junior to maintain the desired level of performance
d) What he/she did to improve the process
e) Steps taken for self-development, if any
The above points are more than sufficient. Testing one's knowledge is fine but then do you have that matured seniors who are capable to assess accurately the replies or presentation by the internal candidates? Please look at the capability of the seniors (without getting carried by their designation) and then take a decision on what method to be adopted.
Final Comments: - Do you have "Policy on Employee Promotion" well in place? I feel that it is not. You need to devise this policy first. You cannot choose the tools of selection in ad hoc manner. There has to be consistency across the board.
Thanks,
Dinesh Divekar