With the Hippodrome build, the Triumph ability makes Byzantine horsemen stronger. Even if HRE goes Meinwerk, in a straight-up fight, the Byzantine horsemen will win when Triumph is active. HRE should not take a fight once Triumph is activated.

Keshiks from the Eastern contract are good in straight horseman vs horseman because of their armor, but HRE has the best spearmen at this stage due to bonus movement speed and the All-Pikes upgrade, so they will do incredible damage to Keshiks.

I think the biggest problem for HRE, especially on a map like this, which can easily drag into Imperial, is there is nothing beyond Imperial Age for HRE. You don't really have a very special late game army. In contrast, the Byzantines do have that.

There's not really a good answer that Byzantines has to Men-at-Arms. He needs to get some Javelins up, but they do okay, they're not hard counters.

If they get the relics that boost the eco and with the relic towers as defense, that could pose a thorny issue for Byzantines.