Main issue with 5 men Grenadiers at this point is stacking on the LMG which would make it one of the strongest infantry units in the game since you'd have to chew through 4 models to reach the LMG and Grenadiers per model have good stats. This is on top of being a snare squad with rifle grenades.
One the ideas we've been thinking of ideas, but it's not the easiest as it might stack too much power, but we will see what turns out.
We've talked about things like faster cap speeds end game after T4 so Ost will start pushing the offensive; reinforce has been discussed, though there was talk about a global cost reduction on Ostheer infantry in reinforce.
Two things:
1) Free medkits for Grens/Pioneers/Osttruppen once T4 is up would be really nice.
2) Why not give them the 5th man at T4, but make it a horrible 5th man? So either let squads upgrade with:
A. 5man Grens upgrade once T4 is up, the 5th model is an Osttruppen model with 1.10 target size and Osttruppen stats in and out of cover. When last model remaining is the Osttruppen model have him fire the LMG42 with the Osttruppen stats.
B. Once T4 is up allow 4man non-LMG42 Grens to receive 2 Osttruppen models and become a 6 man squad that has snare and rifle nade but no weapon slots left.