Personal taste will probably win out here. But if you're making the level IV the standard unit, that means that unit is capable of handling the large majority of needs that may come up. Without armor, I don't see units handling "the large majority of needs." Additionally, what exactly is the goal of these units? In canon material, the ComGuard's unique structure served two key purposes. First, the diverse mix of forces allowed for large units to be broken into much smaller sub-units (level IIs or so) and serve as acceptable garrison forces for a large number of facilities (HPGs). Second, the diverse mix of forces allowed for large units to be hugely effective against the Clans. That's it. As soon as you set those two things aside, the ComGuards really weren't that great of a military. Taking and holding territory? Not something they were built to do. Static defenses of large swathes of territory (like Successor State militaries do)? Again, not something they were built to do.
So I think it's difficult to propose changes without knowing the backdrop. In canon material, we know very clearly the ComGuard's purpose and Focht's effect on them (as Halvagor mentioned). Without knowing that here, we're making blind changes to the ComGuards. Pretty soon, they'll end up resembling the other faction's militaries and lose what makes them unique. They were a military made for a limited number of very specific purposes (and post Tukayyid, pretty much one specific purpose). Their leader played a big part in defining the military. That's one of the reasons why they failed so badly during the Jihad. The Blakists changed and evolved to become an army of conquest. When ComStar tried to do the same thing with Case White (and during the Liberation), they took disproportionally high losses compared to other Coalition armies. They were not an army of conquest.
I mention all that, because it showcases the uniqueness of structure and clarity of purpose that the ComGuards hold as a military. Setting aside specific unit differences, the Successor State militaries are generic militaries. Some specialize in one aspect more than another, but they are all largely built to fulfill a variety of roles (conquest, defense, and raiding). The ComGuards were not built that way. They were built for a specific purpose (a purpose that changed later, once Focht and the Clans got involved) and remained committed to that purpose. Their role as the Battletech version of the U.N. is something that makes them unique. When you are making changes to them, be careful not to lose that uniqueness and simply turn them into another generalist Successor State military. And when you're asking for suggestions without knowing the unique circumstances that form this version of the ComGuards (how Focht plays in, etc.)...it becomes difficult. Those very things are what made the canon ComGuards, the ComGuards.