It wouldn't be a nerf. You would see more snipers mortars/mortars half track , flame pios and smoke in games. That's how we did it vcoh 1. We didn't have a rifle nade and the game worked just fine. Us Wehrmacht players had to use skill and tactics instead of the line infantry clicking a button.
Removing Rifle Grenade would be like removing Oorah, it's a key part of the unit's combat ability. I use that comparison because Grenadiers can use Rifle Grenades to stun a Maxim and try to crawl away, whereas Conscripts can evade an MG by Oorah'ing away. Alternative you could compare it to the Molotov, aka forced decrew / retreat of any support weapon within range.
Why would you ever pick a pg over a g43. G43 are better in every single way except pure at roles. And that is a design issue because you have over lapping roles with core infantry. One is doctorine specific but in many of the most powerfull and used doctrines I may add.
Using the "Grens with Assault Rifles" comparison, you should look into why x4 MP 44's for 60m aren't worth it compared to x2 G43's for 60m. The reason is because less G43's allow for some range, but still give you an incentive to close in, while the MP 44's force you to close in but you can't close in too much or you lose, and if there's no cover nearby you automatically lose. The G43's are more versatile and effective, while the MP 44's are funneled into a role that the unit wielding them isn't great at.
Pg are not terrible. They do exactly what they have done since vcoh. People compare their economics to grenadiers and right now coh2 grenadiers are way more powerfull than vcoh Grenadiers and the difference is the rifle nade added on coh2.
CoH1 Panzer Grenadiers are not comparable at all to CoH2 Panzergrenadiers. CoH1 Panzer Grenadiers start off as the weakest core infantry but slowly become the strongest core infantry as you upgrade them.
Likewise vCoH Grenadiers are not comparable to CoH2 Grenadiers, and CoH1 Grenadiers were
much stronger than CoH2 Grenadiers. CoH1 Grenadiers had higher health than any American or British unit in the game, and were more accurate as well. They came out generally when Americans researched BAR's, but could still counter them with just their Kar 98's, and could get 2 MG 42's to counter any Infantry the Americans or British could throw at them. CoH2's Grenadiers are much weaker in comparison.