Self-explanatory. Brandenburg Gate is a very weak wonder in my opinion for every type of playstyle. For wide militaristic empires, which has plenty of cities thus plenty of supply, experienced troops, and generals, and by the time it becomes available likely multiple vassals, it is useless. For wide progress it still less experience and supply than just building military academies. And a great general for a price of wonder, at the time when far more powerful wonders, especially for wide play, like Eiffel, Neuchsweinstein, or even Slater Mill just for coal, becomes available, is not enough to validate it. I would consider it the most useful for tradition for vital supply, but again, this is very high price for just plus ten supply, as in case of tradition you usually have 200% price for wonders by industrial. I would suggest at least giving it a free military academy as a minimum. And we can either change it completely, or give it more flavour with spawning a free great writer von Clausewitz alongside a general. Or, if happiness or warmongering system be revised (make it harder to mantain) we can give it -1 unhappiness from distress in every city (from mass military conscriptions which basically provides employment and chance of social advancement), and make it quintessntial warmonger choice, but currently it is very easy to mantain happiness in even very wide, militaristic empires, so it would be overkill.