Panzergrenadiers are Ostheer's advanced/elite infantry. Armed with assault rifles they perform well at mid-range against infantry with the capacity to also deal strong close-range DPS that meshes well with their Bundle Grenade. These traits make them good at defending support weapons and forcing enemies to keep at distance where Grenadiers or MG 42s can do the heavy lifting.
When armed with Panzerschrecks, they can deliver large amounts of burst damage and make potent support against flanking vehicles or forcing away units like tank destroyers.
Deployed from the Leichte Mechanized Kompanie, they can arrive when what could be considered the late early-game early-mid game is beginning.
Timing: Panzergrenadiers arrive at a later stage in the game outside certain strategies. By this point, other infantry are getting weapons and/or veterancy, but the biggest thing is that their arrival time coincides when Ostheer generally has 4 squads of Grenadiers who are likely arming with LMGs, veterancy, along with support weapons.
Combined with the fact Grenadiers are easier to micro with their ranged weapons and have utility in the form of snares, it's hard to justify adding them in when you got most of what you need from T1 for your infantry.
Competition in the Tier: T2 has many options for Ostheer to go with. The most chosen first units tend to be light vehicles as they allow Ostheer to go on the offensive and/or punish lone squads, especially those which lack snares or AT weapons.
Panzergrenadiers, meanwhile have all the weaknesses of infantry and will bleed if not handled correctly. They also don't start hitting their stride until veterancy 2-3 and cannot sit back like Obersoldaten.
To make Panzergrenadiers an AT option, you need a lot of munitions which means delays on the medical bunker so its often better to deploy earlier pak guns that also have use in the mid-late game and have a range advantage. You generally will not see early Panzerschrecks; LMGs to win the infantry war and the medical bunker all compete. This munition cost creates choices and delays and should be kept.
Difficult to Use Versus Alternatives: Panzergrenadiers are not a squad you can throw at the enemy in any shape or form. They need to pick their engagement ranges, figure out how to avoid fire on the way in and they be able to stay in the area long enough to deal their damage. Unlike Grenadiers, they don't have the advantage of needing to just keep the enemy at a distance, but they do compensate with having better DPS at the mid-short range can beat units Grenadiers would have issues with at short-range.
Still, in most cases, good MG 42 micro combined with Grenadier's good LMG DPS allows Ostheer to deal damage at distance and forces the enemy to close rather than the other way around which is more difficult for all assault infantry. No one wants to approach PGs and will keep distance where the squad is weakest unlike Grenadiers who have the MG 42 to protect them from assault units.
G43s Need a Revamp: G43s, while very good at chasing down hostiles with minimal DPS lose on the move, along with changing the squad's damage to deal high damage per shot, does not have major improvements. In fact, G43s make them weaker at short-mid range by a considerable margin. Their advantages do not kick in soon enough over the StG 44 unless you want that +7 sight for spotting.
This is me throwing out random ideas. I'm not sure how this unit would see more play without becoming broken without extreme drastic overhauls.
Headquarters Unit after Battlephase: My biggest personal issue with PGs over all others, is timing. When I need to field the MG 42 along with 3-4 Grenadiers in a traditional build before teching up, I really don't need to be fielding more infantry when LMGs allow the Ostheer infantry to compete during the later stages of the mid-game and allow me to hand back.
Being in the HQ means they are not competing as heavily with all the T2 units that are so valuable and it might open new strategies where one holds out for BP 1 with fewer forces or more support weapons. It's somewhat similar to Osttruppen and Assault Grenadiers into T2, but it's more for rushing out a different kind of infantry.
Population Reduction: They're elite/advanced infantry, but given the difficulties to get them into combat, I don't think they need to be 9. Reducing them to 8 I do not think would encourage spam given they lack proper snares, need munitions for AT weapons, and don't have the long-range DPS or Rifle Grenades to destroy HMGs like Grenadiers do.
G43s: Equip the entire squad with G43 Rifles and then boost their mid-range so the advantage over the StG 44 doesn't start at range 25-28. The weapon remains a trade-off, but allow them to have a decisive advantage at a greater range over the the standard StG 44.
What are Yours Ideas?
What do others think of on the unit? PGs, themselves and their stats, I feel are fine as they are a unit that requires some thought to use and have specific purposes. I just think they just come in at a point where the core roster is saturated with a large number of starting infantry, existing choices in infantry/support weapons and competition in their own tier where shock units and/or manpower-based AT weapons take precedence over the unit.