nice to see there are more people who follow this mod.
I have to say though, that I don't think that more unit types for ground fighting are necessary (or even desirable).
We are dealing with a strategic level view, which is quite different from the skirmishing tabletop. When you have a few dozen men and a handful of vehicles it makes a hell of a change if you swap out a Leman Russ for a Hellhound.
When a unit of infantry is (rough estimate) a hundred thousand men (with their organic support, I'd suppose), you just have to assume that a viable mix of assets is present.
Another factor is Command and Control - here on earth the first lesson of warfare is, that men working together as a team can defeat opponents who might be individually and/or in their sum much stronger than they are, but who are fighting as individuals.
This elusive factor would be extremely important to the Imperial Guard, who almost without exception find themselves outmatched man for man.
Chaos on the other hand, while sporting some of the strongest fighters that universe has to offer, would rather tend to just swing until something gives (Khorne Berserkers anyone?).
I'd rather think about what mix of assets each of the units in Distant Worlds represents.
For the imperium (which is the only faction that I can even remotely claim something like solid knowledge), I'd tentatively say:
Armor: Titans of course, but also Baneblades and their brethren (nothing as feeble as a regular tank though). But definitely an Imperator-Titan as an icon.
Special forces: Sororitas, Astartes, Valkyrie-mounted Stormtroopers, arguably regular tanks of the faster types. I don't see Kasrkin in sufficient numbers to be a factor, but maybe I am wrong. Personally I'd like a Valkyrie as an icon here.
PDU's: Atmospheric interceptors, emplaced air defenses - Hydras and the like would be organic support for infantry units (I would say). They'd make a pretty nice icon though, so by the "Rule of Cool" maybe they should be here anyway.
Infantry: Everything else. Guardsmen, Chimeras, Basilisks, Hellhounds and their variants. Have a Squad of Guardsmen for an icon, the poor bastards deserve some recognition.
The other factions might be similarly groupable.
My estimate of a hundred thousand men (or equivalent) is based on the best planets being inhabited by up to 30 billion people (loosely interpreting "people").
I usually invade those with no less than a hundred units, which would be 10 million soldiers (kind of a small garrison if you compare with wartime Vietnam, where allied forces exceeded a million men - and we are talkiong about an itty bitty tiny country here).
So it actually might be closer to a million guys per unit, but the object here is getting a feel for the dimensions we are dealing with.
And even if a unit were to be ten thousand men only - I find it inconceivable to have them out there without a lot of mechanized support.
WANT... MORE... MODDABILITY...