After examining the provinces in ancient Han China, there's only 13 provinces.
With over 35 - 40 Unique characters and a coupled hundreds generic ones, I think the provincial system needs an overhaul.
Province (Governor) > Commandery (Administrator) > County.
1.A Province consists of multiple commanderies (More the better). Clicking on provincial capital will show the commanderies under the provincial jurisdiction. A governor can be appointed and will be the superior officer of all the administrators (commandery) under the province. Has taller walls & bigger garrisons (Refer point 4).
2.A commandery will probably be the equivalent of a province in ToB. Clicking on the Commandery settlement in the campaign map will show the counties around it. An administrator may be appointed but can be left empty. County with administrator will get the administrator buffs and counties without will receive buff from the governor. Has less garrison and slight inferior walls to Provincial capital. Administrator might be given to a lesser character to increase loyalty despite governors having better buff.
3.A County is part of a commandery. Has no garrison. Consists of multiple visible settlements within the commandery borders. Can be sacked and occupied like in ToB. Counties can also be awarded as fiefs to followers who are meritorious but a portion of the tax revenue will be an opportunity cost. "Special" counties may award the title "Marquis of ABC county" and additional fiefs may be given to existing marquis.
4.There's another issue in my mind right now and has bothered me since Rome 2 till Warhammer. Sieges are too easy especially on smaller settlements. I hope Provincial capital in 3K are really hard to occupy even in easy mode. One way to make the mechanic interesting is, players must occupy the commanderies in order to weaken the defenses of the provincial capital. Say, there are 10 commanderies in a province, each commandery occupied will reduce the provincial capital strength by 5% hence occupying all 10 will reduce the strength by 50% of the provincial capital and will make the siege easier. However, the AI must make attempts to recapture the commanderies and defend it. Commanderies may also raise army to aid a besieged Provincial Capital.