While a Fast Castle strategy is currently in vogue, most players opt for a Fast Imperial (Fast Imp) approach when playing as the HRE. In my view, this is because: 1) these civilizations struggle to exert significant pressure during the Feudal Age, and 2) the Fast Imperial strategy becomes a highly attractive option in the Castle Age, thanks to the Palace of Swabia.
This implies that the HRE’s alternatives for staying in the Feudal Age are relatively weak. How might this issue be addressed? Could they be granted a new unique technology that provides a combat advantage? Or perhaps allowing them to construct churches as early as the Feudal Age? Could building the Aachen Chapel unlock the “Cistercian Churches” technology during the Feudal Age? And if the Aachen Chapel were to become more useful, could the Meinwerk Palace be given a better unique upgrade to compensate?
Looking at it this way, it’s clear that the HRE currently has very little reason to stay in the Feudal Age. Unless you go for a Fast Imp and overwhelm your opponent through sheer superiority in scale, there’s simply no other way for HRE.