Meinwerk Palace provides cheaper, faster technologies, so horsemen and spearmen will deal a lot more damage, which is very beneficial against any potential feudal age all-ins from House of Lancaster.

The villagers of House of Lancaster still have the short bow ability; in a fight against HRE's feudal spearmen, those short bows can make a big difference.

Yeoman archers are baseline a little bit faster, but still not as fast as HRE archers; however, they have one more tile of range.

Heavy Maces is already in. You prioritize it as HRE if your opponent has Lords.

The weird thing with these type of civs where they have a military landmark essentially — they don't need to invest wood. They get their harassers free. So I think opening of feudal should favor House of Lancaster.