You are trying to use definitions that don't apply to the licensing requirement. TC § 55-50-301(a)(1) states:
(1) No person, except those expressly exempted in this section, shall drive any motor vehicle upon a highway in this state unless the person has a valid driver license under this chapter for the type or class of vehicle being driven;
Thus, what matters is the definition of motor vehicle. The definition that applies for the purposes of driver's licenses is found in TC § 55-50-102(37), which states:
(37) “Motor vehicle” means a vehicle, low speed vehicle or medium speed vehicle as defined in this section, machine, tractor, trailer or semitrailer propelled or drawn by mechanical power used on highways or any other vehicle required to be registered under the laws of this state, but does not include any vehicle, machine, tractor, trailer or semitrailer operated exclusively on a rail;
Moreover, vehicle is defined in subsection (56) as follows:
(56) “Vehicle” means every device in, upon, or by which any person or property is or may be transported or drawn upon a public highway, excepting devices moved by human power or used exclusively upon stationary rails or tracks;
Those are the only definitions that matter when determining whether you need a license for whatever it is you are driving. And they are very broad definitions. Most significantly, nothing in either the the definition of vehicle or motor vehicle limits them to commercial vehicles. Regular passenger cars and trucks are covered by those definitions. Indeed, even using an off road vehicle on the highways requires a license, even though such machines are not commercial vehicles. The Tennessee Attorney general in a written opinion explains:
1. Any person driving “any motor vehicle” on a highway in Tennessee must have a valid driver's license. See Tenn. Code Ann. § 55-50-301(a)(1). A reading of our statutes reveals that an off-highway vehicle qualifies as a motor vehicle. State law requires every person driving “any motor vehicle upon a highway in this state” to have a valid driver's license for the type or class of vehicle being driven. Tenn. Code Ann. § 55-50-301(a)(1). “Motor vehicle” is defined as a “vehicle, low speed vehicle or medium speed vehicle as defined in this section ....” Tenn. Code Ann. § 55-50-102(34). “Vehicle” is defined as “every device, in, upon, or by which any person ... is or may be transported ... upon a public highway, excepting devices moved by human power or used exclusively upon stationary rails or tracks ....” Tenn. Code Ann. § 55-50-102(53). A Class D license is required for the operation of any vehicle weighing less than twenty-six thousand one pounds. See Tenn. Code Ann. § 55-50-102(19)(D). Because “motor vehicle” and “vehicle” are broadly defined in the statute, an off-highway vehicle such as a four-wheeler is a “motor vehicle” under Tenn. Code Ann. § 55-50-301(a)(1). For this reason, any person operating an off-highway vehicle upon a highway in Tennessee is required to have a valid driver's license.
Tenn. Op. Att'y Gen. No. 09-164 (Oct. 14, 2009). So you aren't going to win on an argument that driver's licenses are only required when driving commercially. The Tennessee statutes are not so restricted. As the Attorney General states, the definitions in the statute are quite broad.