If the all the docs are in-network as you say, it doesn't matter what you charge, they will all get paid the same amount per the various insurance's fee schedule. As an example, if BCBS allows $100 for a 99213, they will allow that regardless of what doctor is billing it, and how long they have been a doctor.
You want ONE fee schedule. And the fees on it should reflect what the highest allowable is for any given insurance, rounded up however much you want. As an example again, BCBS in my area allows more than any other insurance we bill for a 99213. So our fee for that is charge is $120, based on their allowable, and rounded up to the nearest whole dollar.
If you want to pay doctors in your practice a higher percentage based on tenure, then just do that. While I wouldn't recommend it, it is an option. For instance: 1-5 years gets 35%, 6-10 years gets 40%, etc, etc. But truly, regardless of whether a doctor has been practicing for 1 year, or for 8 years, they should get the same percentage. They are doing the same work for the same money.