My greetings to ROP section of the forum.
In ROP all non-Prussian grenadiers units including Prussian allies Hanoverians and Brunswickers have decreased speed of movement (90% of normal). It hinders allied operations and makes usual 15% Prussian marching advantage even greater (at the same time Prussian grenadier and line units rather illogically march at the same pace in the game).
By the time of SYW grenadiers were regarded as heavy infantry not for the weight of their equipment but for the punch they could inflict upon the enemy. Grenadiers abandoned their hand grenades in supply trains and rarely used them (usually assaulting/defending fortifications).
As shock troops grenadiers were organized in compact and maneuverable formations (battalion organization, fewer men in companies, lighter trains) and commanded by best officers. Being picked from the ranks for their physical strength, bravery and initiative grenadiers participated in most dangerous and daring exploits of SYW(Laudon's famous Grenadier Corps comes to my mind). So far I can't understand why grenadiers in ROP move slower than plain line infantry.
I think that synchronizing marching speed of non-Prussian line and grenadier units would be logical and may affect ROP gameplay positively.