Your H1B extension on your approved I-140 should have no impact. Most of your roles remain the same. Ensure you provide most of your job duties from your previous H1B/H1B extension and add new additional roles.

Now for your I-140, as per my attorney, a promotion to a more senior or a team leader shouldn't be an issue if your 50% of job duties remain the same and unless you are getting promoted to a manager position.

You are saying you will be a team lead but then you are also saying you will have 6 direct reports. If you are just going to lead these 6 people as a team leader then that is okay but if are going to have any direct report or you are managing even one of the people then you are also a Manager. The devil is in the role you play and the term you use.

Promotion to the Manager role will have a 100% impact on your I-485 but not on your H1-B. If your priority date is closer and you want to use your existing I-140 for filing I-485, then I would refrain from such a promotion. Believe me, you will not be alone. Many including me have done such sacrifices for securing GC. Being H1b/L1 and their dependent is a curse for people born in India/China. It's a question of whether you want a GC or a promotion that impacts I-140 and how far are you from the filing date.

But if your priority date is further than 1 year then you can restart your perm process from scratch as a manager and you will get your old priority date. Its from scratch, so it will take a good one year.