Simplest way to represent similar infantry unit would be mix of motorized rifle and SRM infantry, or mechanized (tracked or wheeled) equivalents. How large is your unit? A simple company of infantry could be two platoons of rifle and one platoon of SRM infantry, type as fits your ideas best.
These are included in Total Warfare book by default (spread across several tables, BV can be acquired from MUL if relevant, eg
Motorized SRM platoon), so you don't need to make anything if you don't mind using generic infantry, just copy relevant data to infantry record sheet.
I think there used to be pre-filled generic infantry record sheets available but if they still are, i can't find them.
Alternatively TRO 3085 and its Supplemental contain a lot of more elaborate pre-made infantry, some might suit your needs.
Infantry use is pretty simple. They may have variety of weapons and whatever else, but in practice all those are condensed into single damage value (with pretty arbitrary maximum range) that degrades as the infantry unit takes damage (1 damage=one dead trooper). They take a lot of damage easily too.
Type determines movement speed and terrain restrictions but is very abstracted. Mechanzied infantry can move into buildings for example. Weapons can also have restrictions, SRM foot infantry for example can only move or attack, not both due to encumbering nature of their weapons.
In standard play infantry moves by platoons, which is kinda silly from realism perspective, but then again they're not focus of this game at all. Tactical Operations has rules for squad-based on infantry (basically you make several smaller infantry "platoons" that are more difficult to hit).
https://bg.battletech.com/forums/index.php/topic,20252.0.htmlThis article goes into more in-depth about infantry. Might be useful.
Also as reminder, infantry rules start on page 212 or thereabouts in Total Warfare.
